Tetzaveh (5764)

From the book Mida Tova: Articles on the Hermeneutical Principles by Rabbi Michael Avraham. Translated from Hebrew using gpt-5.4 (reasoning_effort=high, batch API).

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With God’s help. Midah Tovah — eve of the holy Sabbath, Parashat Tetzaveh, 5765.

Questions

1. Are there mitzvot (commandments) that do not apply across generations?
2. Is the eternity of the Torah a foundational principle, or the result of a derivation?
3. The two types of the common-denominator derivation.
4. What is the difference between a binyan av (construction of a general principle) from one verse and a binyan av from two verses?
5. How can one derive from two verses that come as one?
6. Three reasons why tzrichuta, the mutual necessity of the two source texts, is needed as the basis for carrying out a common-denominator derivation.
7. What does tzrichuta have to do with the requirement of diversity in evidence as a basis for scientific generalization?
8. Two approaches in the philosophy of science: actualism and informativism.

Hermeneutical Principles

• Binyan av from two verses.
• The common-denominator derivation.
• The rule that two verses that come as one do not teach beyond themselves.

A. From Where Do We Derive the Principle of the Torah’s Eternity?

“How is a binyan av from two verses made? The section of the lamps is not like the section of sending away the impure, and the section of sending away the impure is not like the section of the lamps. Their common denominator is that in both of them Scripture uses the word tzav, and they apply immediately and for future generations. So too, anything stated with the word tzav applies immediately and for future generations.”

Illustrative Baraita, at the beginning of Sifra

“The section of the lamps is not like the section of sending away the impure, and the section of sending away the impure is not like the section of the lamps. Had the section of sending away the impure not been stated, I would have learned it from the section of the lamps. Why, then, was it taught here? Because many things could be taught from it. Thus, their common denominator is that in both of them Scripture uses the word tzav, and they apply immediately and for future generations. So too, everything stated with the word tzav applies immediately and for future generations.”

Jerusalem Talmud, Bava Kamma 1:1

Introduction

We have already mentioned that at the beginning of Sifra there appears the baraita of Rabbi Ishmael’s thirteen principles. Immediately after it comes the Illustrative Baraita, which presents examples for each of the principles on that list. The example for the principle of binyan av from two verses is taken from our parashah, and it looks like a derivation by way of the common denominator.

On the page for Parashat Shemot we dealt with the common-denominator derivation and described several possible schemes for understanding how it works. We noted there that the medieval authorities disagreed whether “binyan av from two verses” is simply another name for the principle of the common denominator, or “what is the common side?” as held by Rashi, Rabbi Saadia Gaon, and the Raavad, or whether it is the name of a special kind of common-denominator derivation: one in which the two source texts appear in different contexts. See Sefer Keritut, the section Beit Middot, subsection Beit D.

In the Yerushalmi cited above, the derivation looks a bit different. The section of sending away the impure is not unique; it can be learned from the section of the lamps. Precisely because it can be learned from the other section, it is unclear why it is repeated at all. From this the expositor concludes that it was apparently written so that we might learn from it, together with the section of the lamps, about the rest of the Torah.

Description of the Derivation in the Illustrative Baraita, and Its Difficulties

The derivation before us teaches that commandments in the Torah are immediately binding and remain binding for future generations on the basis of two source texts, both of which use the word tzav: the sending away of the impure, outside the camp, or later outside the Temple, and the lighting of the lamps in the menorah.

The formulation of the derivation is unusual, and unlike other formulations of the common denominator. For some reason, precisely this formulation was chosen as the canonical example that best demonstrates the pattern of binyan av from two verses. Usually, a common-denominator derivation begins with an attempt to derive from one source text. That is then met by an objection, which both displays the unique feature of that source and explains why a second source is needed in order to reach the general conclusion. After that, the second source is introduced, resolving the problem in one of the ways we described on the page for Parashat Shemot. For what follows, let us spell out the difficulties in this midrash (rabbinic interpretive derivation) one by one:

1. It is not clear why one cannot derive from each of the two source texts separately to all the other commandments. In other words, why do we need a second source and a common denominator at all? Why is a binyan av from one verse insufficient?
2. The midrash does not explain what is unique about each source text, or why each is “not like” the other.
3. It is not clear how we know that these two commandments themselves in fact apply immediately and for future generations.
4. Why would it even occur to us that other commandments might not apply for future generations? Is not the Torah, by its very nature, wholly a set of commands for all generations?¹
5. If a commandment is not introduced by the word tzav, does it then not apply for future generations? There are quite a few such commandments in the Torah, and in practice we observe them for future generations as well.

Description of the Yerushalmi’s Derivation, and Its Difficulties

In the Yerushalmi, it appears that the verses about sending away the impure are superfluous, since they could have been learned from the section of the lamps. Of course, the meaning is not that we could have learned the basic law requiring the sending away of the impure, but rather that we could have learned that this command applies immediately and for future generations. In other words, what is superfluous is not the section about sending away the impure itself, but the explicit instruction that it applies immediately and for future generations, an instruction that was stated both in the section of the lamps and here as well.²

Yet this raises a principled difficulty in understanding the Yerushalmi’s derivation. If indeed one verse is superfluous, then it cannot serve in a common-denominator derivation. A condition for such a derivation is that each source text have a unique feature of its own, as we saw on the page for Parashat Shemot.

In fact, the question is even stronger. If one of them is indeed superfluous, then we face the problem of the rule that two verses that come as one do not teach beyond themselves. Only if both verses are needed can one learn from them to the rest of the Torah. But if one is superfluous, then it is obvious that they were written to teach us that the relevant law applies only to them themselves. Their very inclusion is meant precisely to prevent us from extending that law from them to the rest of the Torah. On this, see the page for Parashat Toledot, part 2. It is therefore unclear how the Yerushalmi infers from the redundancy of the passage about sending away the impure the exact opposite conclusion: that one may learn this to the whole Torah.

The Technical Questions about the Baraita’s Derivation

The first three questions are mainly technical. The third arose in our discussion of the Yerushalmi, and one can consult the commentators on the midrash about it. As to the first two questions, the medieval authorities already discussed them at length, and each offered different reasons for the uniqueness of these two commandments, both one relative to the other and each relative to the rest of the Torah. It is worth noting that usually it is the same unique feature: whatever prevents us from learning from source A to the rest of the Torah also distinguishes it from source B, and vice versa. For example, the Raavad explains in his commentary to the Illustrative Baraita that the sending away of the impure is unique in that its violation incurs karet, that is, excision, and therefore one cannot derive from it to the lamps or to the rest of the Torah. The lighting of the lamps, by contrast, is unique, the Raavad explains, because it is frequent, since the lamps must be lit every day, and therefore one cannot derive from it to the sending away of the impure or to the rest of the Torah.

We are thus left only with the two substantive questions about the baraita’s derivation, questions 4 and 5. These bear directly on the issue of the Torah’s eternity, to which we now turn.

The Eternity of the Torah

There are two possible ways to understand the fact that proof is needed that the commands under discussion apply for future generations:

1. There is some special reason that could lead us to conclude that these particular commands were not stated for all generations. Presumably this reason lies in the very use of the word tzav. Specifically with commandments stated in the language of tzav, one might have thought that they were said only for the immediate moment, and therefore specifically there proof is needed that they were said for future generations as well. All other commandments were certainly said for future generations, and we could not have thought otherwise about them.
2. In truth, with respect to all commandments one could have entertained the possibility that they do not apply across generations. The conclusion of our midrash teaches us that this is not so. On this reading, the conclusion of the midrash concerns not only commandments whose wording includes the word tzav, but all commandments whatsoever. Thus, in the end, all the commands of the Torah are indeed for future generations, but we learn that from this very midrash.

Both of these directions appear in the Raavad’s commentary to the Illustrative Baraita. This is his language:

“If you ask: why does the tanna here count this under binyan av? He should have counted it under verbal analogy, a gezerah shavah, since we learn it from the word tzav. One may answer that this is because tzav is not an extra term available for such a comparison… But a better answer than that is that the tanna learns from the lamps and from sending away the impure that the whole Torah is immediately binding and binding for future generations. He does not refer only to those passages in which tzav is written, but to all the commandments in the Torah, which are all called commandments. And when he says here, ‘their common denominator is that they are with tzav,’ he does not mean the specific word tzav; he means the category of command…”

The Raavad begins by asking why the baraita presents this derivation as an example of binyan av from two verses rather than of verbal analogy, since the midrash is based on the appearance of the word tzav in both contexts. Here the Raavad assumes that the midrash really does use the word tzav itself, and apparently that its conclusions therefore concern only additional contexts in which the word tzav appears.³ From this he concludes that what we have here is verbal analogy, not the common denominator.

To be sure, that assumption itself seems to need explanation. Why not say that the common denominator here is built from a combination of two verbal analogies? In note 1 on the page for Parashat Shemot, we assumed that the common denominator is based only on an a fortiori argument, a kal va-homer, or on binyan av. Now we see that the Raavad states this explicitly. If this is the structure of a common-denominator derivation, then it is not verbal analogy, and conversely. This itself is an important conclusion from the Raavad’s words here, though it still requires study and systematic examination.

In his answer, the Raavad raises the two directions we presented above:

1. The word tzav is not an extra term available for comparison, and therefore this is not verbal analogy. See the page from last week, where we mentioned the dispute in Babylonian Talmud, Niddah 22b-23a, over whether one expounds a verbal analogy when the relevant word is not extra. It appears that the Raavad rules here that one does not. On this reading, the assumption of the question remains in place: the derivation concerns only contexts in which the word tzav appears, exactly as in option 1 above.
2. The derivation does not concern the word tzav at all, but all the commands in the Torah, exactly as in option 2 above.

According to option 1, the eternity of the Torah and its commands is self-evident. Only commands in which the word tzav appears could be understood as instructions for the immediate audience alone: Moses is asked to command the Israelites standing before him, not the people of Israel throughout its generations. Therefore the Sages derive by binyan av from two verses that even such commands were said for future generations.

According to option 2, the eternity of the Torah itself is learned from this midrash. If so, we have here a very fundamental midrash within Jewish faith as a whole: only from it do we learn that the commands of the Torah are eternal. That is a striking claim. A midrash of halakha (Jewish law) teaches us one of the principles of faith, namely Maimonides’ ninth principle in his introduction to Perek Helek:

“The ninth principle is non-abrogation: this Torah of Moses will never be nullified, and no other Torah will come from God besides it. Nothing may be added to it and nothing taken from it, neither in the written text nor in its interpretation, as it says: ‘You shall not add to it and you shall not diminish from it.’ We have already explained what needed to be explained concerning this principle in the introduction to this work.”

Summary

We have therefore arrived at what seems to be a satisfactory understanding of the derivation in the Illustrative Baraita. Even so, it is still not entirely clear why it does not specify the unique properties of each of the two source texts. Its wording still seems not fully deciphered.

Beyond that, one further task remains: to understand the Yerushalmi’s derivation, and in particular the difficulty we raised with respect to the rule that two verses that come as one do not teach beyond themselves. In the end, it may turn out that this will also shed additional light on the baraita’s derivation.

B. The Common-Denominator Derivation versus the Rule That Two Verses That Come as One Do Not Teach Beyond Themselves

Introduction: Why Tzrichuta Is Necessary

The logical and hermeneutic basis of the common-denominator derivation tells us that when there are two verses teaching the same principle, one may learn from them to all the other contexts in the Torah. On the other hand, the logical and hermeneutic basis of the rule that two verses that come as one do not teach beyond themselves appears to tell us precisely the opposite: if there are two verses teaching exactly the same principle, then clearly they teach only about themselves and not about the rest of the Torah. At first glance, then, there is a frontal contradiction between these two logics.

To understand the difference between them, we must note that whenever there is a common-denominator derivation, each of the source texts has its own unique feature, a feature that prevents us from learning from it to the rest of the Torah, including the other source text. This two-sided distinctiveness is called tzrichuta in talmudic language.

At first glance, tzrichuta is required only to explain why one source text is insufficient, that is, why we need the second source. In that sense, tzrichuta is only the motivation for performing a common-denominator derivation. But we can now see that this is not the whole picture. Tzrichuta is also needed to prevent the activation of the principle that two verses that come as one do not teach beyond themselves.

The rule of two verses is based on the consideration that if the two verses really teach the same principle, then one of them is superfluous. The fact that it was nevertheless written teaches us that the Torah wishes to tell us that the principle under discussion is relevant only to these two cases and not to the rest of the Torah. Tzrichuta, then, is not only the motivation for performing a common-denominator derivation; it is also a condition for being able to do so. Without tzrichuta, not only is such a derivation unnecessary; it cannot even be performed. In the absence of tzrichuta, the rule of two verses is triggered, according to which the two verses are exceptional and therefore cannot teach about other contexts in the Torah.

As noted, our derivation serves in the Illustrative Baraita as the canonical example of binyan av from two verses. It is therefore no surprise that the Raavad himself, and likewise Sefer Keritut in the subsection cited above, explains precisely this foundational principle of how the common denominator works, specifically with respect to our derivation:

“And both of them teach the other commands in the Torah, that they are immediately binding and binding for future generations… and this is not a case of two verses that come as one, for both are needed, as we say…”⁴

Tzrichuta in the common denominator is required so that the possibility of generalizing to the rest of the Torah is not neutralized by the rule of two verses.

The Yerushalmi’s Derivation: No Need for Formal Necessity

In light of the previous paragraph, the difficulty posed by the Yerushalmi’s derivation becomes even sharper. All the Yerushalmi tells us is that because the second verse is superfluous, we therefore generalize the conclusion to the whole Torah. At first glance, this is a frontal clash with the rules we have just learned. When one of the verses is superfluous, the operative principle should not be the common denominator but precisely the rule of two verses. How, then, are we to understand this puzzling logic, which seems completely inverted relative to the accepted methods of interpretation?⁵

It therefore seems that the Yerushalmi means something different from what appears at first glance. To understand it, we must explain that there is another possible way to understand why tzrichuta between two source texts is needed. We can clarify this through a brief discussion in the philosophy of science.

A Brief Introduction to the Philosophy of Science: Actualism and Informativism

As is well known, all of science is based on generalizations. We encounter several particular facts in reality, whether natural reality or experimental reality, and infer from them a general law. Generalization from the particular to the general is called induction, as we noted on the page for Parashat Noah, and therefore this process is usually called scientific induction.⁶

The inductive process raises many questions. What is the basis for the validity of such a generalization? For example, if we have seen several times that the force acting on a body is proportional to its acceleration, how can we know that this is an essential feature of the relation between forces and the accelerations they produce, that is, Newton’s second law? Or again: if we have seen several black ravens, how can we know that black is a characteristic of all ravens? What entitles us to draw speculative conclusions of this kind, conclusions about events we have not observed at all?

More than that: why do we regard some generalizations as valid, though not utterly necessary, while other generalizations strike us as wholly speculative? What distinguishes these cases from one another?

Philosophers of science devote much attention to these questions. The positions that have arisen on this issue can be divided into two main camps: actualism and informativism. The terminology is taken from Zeev Bechler’s book Shalosh Mahapekhot Kopernikaiyot, which deals mainly with these questions and their implications.⁷

The actualist approach treats as valid only facts that have actually been present before our eyes. Generalizations are nothing more than products of our overheated imagination. They may be useful instruments for organizing the totality of facts, but they say nothing about the world as such. In themselves, beyond the particular facts, they contain no information. According to this approach, the laws of nature are merely elegant ways of arranging the totality of particular facts known to us. For example, the scientific theory stating that all ravens are black means no more than that all the ravens we have seen up to now are black. The prediction that the next raven we meet will also be black is only a manner of speaking, really just a conditional statement: if the next raven is not black, I will replace the generalization I am currently using, since it will no longer fit the totality of facts I have actually encountered. A genuine actualist, and in truth it is doubtful whether there is really such a creature, cannot predict in any way what the color of the next raven will in fact be.

The informativist approach, by contrast, holds that generalizations really do contain information about the world. The informativist will therefore be able to wager with a very high degree of confidence that the next raven he encounters will also be black.

Actualism is a problematic approach for many reasons.⁸ Because of lack of space, we shall point here only to the fact that it runs entirely against the intuition of any reasonable person. Yet there is a basic problem with that intuition. After a bit of thought, actualism seems correct. How, after all, can we validate conclusions about events or objects we have never seen? That is the main motivation for adhering to an approach so contrary to our intuition. On the other hand, science works. Everyone is willing to wager with very high confidence that the next raven he encounters will be black. This is not just a prediction, that is, a claim open to empirical testing; it is a claim we actually believe.

The Basis of Informativism and Its Limits: Variety in the Evidence

To solve this difficult problem, we must assume, following Husserl’s phenomenological teaching, that we have the ability to discern the general law through the particular facts.⁹ The particular occurrences are, as it were, transparent to us, and through them we see the general law that stands behind them. Our conviction regarding the general law stems from the fact that we simply see it.

Of course, this seeing is not carried out through the eyes, but through some kind of intuitive power of apprehension. That power is somewhat vague, and therefore it requires reinforcement and confirmation. Such confirmation is achieved by subjecting the general law under discussion to different tests. The more tests it withstands, the more confirmed it is in the eyes of the informativist.

Up to this point we have seen that the quantity of evidence is a primary witness to the validity of the generalization. Another aspect that helps confirmation is variety in the evidence. The more varied the evidence, the greater its specific weight. A great many pieces of evidence of exactly the same kind strengthen the generalization only within the domain that was actually examined. For example, if all our observations were made only in Australia, and all the ravens we saw there were black, it would be difficult to conclude from this that all the ravens in the world are black. Perhaps that is a unique feature of Australian ravens. Examining a few ravens on other continents is more important for this generalization than observing a very large number of additional ravens in Australia.

Back to the Methods of Interpretation: Another Aspect of Tzrichuta

In many respects, the work of the expositor and interpreter in the Torah resembles that of the scientist with respect to reality.¹⁰ The expositor examines the examples given to us in the Torah and tries to extract from them a general law. This is the essence of the rule of binyan av, especially binyan av from two verses, as we shall see below. It seeks to identify the shared “parent principle,” as explained on the page for Parashat Shemot, behind several particular cases. For example, the expositor sees that both in the section of the lamps and in the section of sending away the impure there appears the principle that they were stated as immediately binding and binding for future generations, and he wishes to generalize and establish this as a general law valid for all commandments.

We can now understand that there is an acute need for variety in the examples that ground the midrashic generalization. If we use two source texts of exactly the same character, we can always dismiss the generalization and say that it is only an artificial result, that is, an artifact, of the special case we observed. The more varied the examples, the more valid the generalization becomes.

It should be noted that in halakha one cannot adopt an actualist stance. As long as we have not encountered a refutation, a pirkha, that is, an “experiment,” meaning an observation of a halakhic fact that would disprove the generalization, we rely on it and establish legal rulings that may involve Sabbath desecration, karet, various punishments, including capital punishment, and the like. Halakhic informativism therefore requires reasonable confirmation. For that, variety in the evidence is necessary. Our two source texts, which form the basis for the halakhic generalization, must differ from one another in order to increase our confidence in the generalization we have made, namely the binyan av.

This is an additional reason, a third one, why tzrichuta between the two source texts is needed in order to make the common-denominator generalization.

Implication: The Character of Tzrichuta

Even so, it seems that the consideration of variety in the evidence does not require tzrichuta specifically in its standard halakhic sense. In order to increase variety in the evidence, it is enough to show the law under discussion in several different contexts, where the difference between them is varied enough to better confirm the generalization. There is no need for strict formal tzrichuta, that is, for finding a unique feature in each case such that one could not have learned one from the other. If tzrichuta is needed only as an indication of variety in the evidence, as the basis for a better generalization, then it is enough that the two contexts differ, even if that difference is not formal tzrichuta.

When, then, does binyan av from two verses require formal tzrichuta, and when does it require only informal variety? It seems that when a generalization needs strengthening, not necessarily because of a possible objection but because of its importance, or because of our uncertainty about its validity, then we will tend to reinforce it by using varied source texts.

If the generalization is already plausible and the only issue is possible objections to it, then we use the formal structure of the common denominator, and that does require the presence of formal tzrichuta between the source texts.

Back to the Derivations

We can now return to the Yerushalmi and understand it. The Yerushalmi seeks to make a generalization: that all the commands of the Torah are immediately binding and binding for future generations. We have seen that this generalization concerns principles of faith and the foundations of halakha and the worship of God. Such a generalization requires reinforcement, not necessarily because some objection is liable to arise against it, but in order to ground and strengthen so central a claim.

Therefore the Yerushalmi brings two source texts that are not needed in the formal sense. These two sections are not endowed with a kind of uniqueness that would prevent learning one from the other. Nevertheless, the difference between them can certainly strengthen our generalization. Sending away the impure and lighting a lamp do not appear to be connected in any respect. Not because of one unique feature or another, but because the very difference between them creates a variety that makes our generalization more credible. This, it seems, is the Yerushalmi’s intention.

If this is the common denominator in the non-formal sense, then the rule that two verses that come as one do not teach beyond themselves cannot refute it. The two verses are needed because a generalization that is so basic and important requires variety in the evidence. Once that is so, one cannot say that one of them is superfluous and invoke the rule of two verses against the common denominator.

Perhaps the Illustrative Baraita can also be understood in this way. We asked why the baraita does not spell out the uniqueness of each of the source texts. In light of what we have said, it is possible that the baraita, too, understood the matter as the Yerushalmi did, and therefore had no need to specify the unique feature of each source. It is enough for us to see that the two contexts are unrelated in any respect, and that itself strengthens the generalization. For that purpose, it is enough to say:

“The section of the lamps is not like the section of sending away the impure, and the section of sending away the impure is not like the section of the lamps.”

Here there is no need to describe precisely in what respect the two differ, because the consideration at work here is not one meant to prevent the activation of the rule that two verses that come as one do not teach beyond themselves. The consideration here is only to show that the commands in the Torah are immediately binding and binding for future generations, regardless of any unique property they may have.

It should be noted that the Raavad, who ultimately understood the derivation as a formal common denominator, and therefore raised the possibility that it deals only with commandments stated with the word tzav and not with all commandments, since in his view it does not introduce a principle of faith, explains that the tzrichuta is meant only to prevent the activation of the rule of two verses. That is why he also takes the trouble to specify the concrete characteristics of each source text; in his view the tzrichuta is formal. According to his approach, the baraita indeed did not spell out these characteristics, but that omission is not necessarily significant.

If so, the Raavad apparently did not understand the matter as we do. Is there nevertheless some source among the medieval authorities for such a conception?

Sources for This Innovation in the Literature of Rules

We mentioned at the beginning that there is a group among the medieval authorities that understands both forms of binyan av as based on the common denominator; see also the page for Parashat Shemot. The difference between them, on this view, is only whether the two source texts are taken from the same verse or the same context, or whether they are drawn from two different contexts. What is the meaning of this distinction? Why is it important that the two sources come from two different contexts? If the point were formal tzrichuta between them, then that would be true even in binyan av from one verse, for otherwise one could not carry out a common-denominator derivation within binyan av from one verse. Therefore it is clear that what matters is that the material is drawn from two different contexts, quite apart from whether there is formal tzrichuta between them.

According to our explanation, this is precisely their intention. The tzrichuta in binyan av from one verse is meant to prevent the activation of the rule that two verses that come as one do not teach. Therefore what matters there is formal tzrichuta, meaning that each source must have a unique feature. But in binyan av from two verses, a different kind of tzrichuta is required, a non-formal one: variety in the evidence. The two verses are taken from two contexts in order to show that the principle being learned is valid independently of any specific context, and not in order formally to prevent the activation of the rule of two verses.¹¹

We can now understand why precisely a derivation so different in its wording, and with so many difficulties, was chosen as the canonical example of binyan av from two verses. Since what is learned here is a principle that is itself an article of faith and the foundation of halakha and of the entire service of God, we must use a well-grounded generalization. For that purpose, we bring two verses from two different contexts, not necessarily ones that exhibit formal tzrichuta between them, but almost the reverse: in order to show that the main point here is not formal tzrichuta but variety in the evidence. This is exactly the example that shows that most clearly.

A study of Sefer Keritut in the subsection cited above suggests that this may indeed be what it means. Here we should fulfill the saying of the wisest of men: “Give to the wise, and he will become wiser…” Proverbs 9:9.

Footnotes