Question

Again, greetings and blessings to his honored eminence, the great and mighty gaon, Rabbi Michael Abraham, may he live long and well, Maimonides wrote (Laws of Leavened Food and Matzah 1:7): “One who eats any amount whatsoever of leaven itself on Passover—this is prohibited by Torah law, as it says (Exodus 13:3), ‘No leavened food shall be eaten.’ Even so, he is liable to karet or to bring a sacrifice only for the requisite measure, which is an olive’s bulk.” End quote. The Kesef Mishneh and the Mishneh LaMelekh there asked: why did Maimonides need to find a source for the prohibition of eating less than the requisite measure of leavened food? After all, we rule like Rabbi Yohanan (Yoma 74a) that half a measure is prohibited by Torah law in all Torah prohibitions. If so, what is different about eating leavened food that it requires a special inclusive derivation? Another difficulty: how did Maimonides innovate this derivation on his own? The Tzelach (Pesahim 44a, s.v. “ve-od”) answered that from this verse the Sages derived the prohibition against deriving benefit from leavened food, as explained in the Talmud (Pesahim 21b); and in a prohibition of benefit there is no measure of an olive’s bulk. Consequently, eating half a measure is no worse than deriving benefit. The practical difference would be where the rule of half a measure in eating does not apply—for example, if one ate half an olive’s bulk of leavened food close to the end of Passover, such that it cannot combine with another half-olive’s bulk, in which case it is not prohibited on the basis of half a measure in eating, but it is prohibited on the basis of deriving benefit, which has no minimum measure. However, from the words of the Maggid Mishneh there it appears that he understood Maimonides to hold that the prohibition of half a measure regarding leavened food is nothing more than the ordinary prohibition of half a measure found throughout the Torah, and not because of deriving benefit. If so, it still remains puzzling why Maimonides needed to find a special source for the prohibition of half a measure in eating leavened food, rather than being satisfied with the general rule of half a measure that applies throughout the entire Torah.   

Signed,
The least of men, A.