Interest on things

Here is chatgpt's response to the issue
First, it is important to know that any discussion on the subject of interest (and in particular "interest on things") is a complex and sensitive halachic matter, and sometimes there are fine details that may vary from case to case. Therefore, if you have a practical doubt or a specific question about how to proceed, it is recommended to consult a rabbi who is familiar with the laws of interest, in order to receive guidance that is appropriate for your specific situation.

Still, in general:

Definition of interest
Prohibited interest refers to an addition (monetary or equivalent) that the borrower gives to the lender by virtue of the loan itself, beyond the loan principal itself. This can be a direct monetary addition, but also a benefit or actual service that the borrower would not normally provide if it were not for the loan.

“Usury of things”
There is a concept in halakha called “usury of things” – when the borrower gives the lender special treatment or exaggerated praise, for which it is clear to everyone that the sole reason is the loan (i.e., he would not have done so at all without the debt). For example, if a person was not accustomed to greeting the lender or calling him by certain honorific titles, and suddenly after the loan begins to do so excessively, with the intention of “returning” a favor for the loan.
However, not every expression of gratitude or good treatment is automatically considered usury of things. There is a balance here between natural and legitimate gratitude, and giving excessive treatment that is perceived as actual consideration.

Is patronizing and praising the lender considered usury?

Basic gratitude (saying thank you, telling friends that he helped you, rejoicing when he succeeds, etc.) – is not considered forbidden usury. This is a human and natural step of gratitude, and in most cases there is no monetary/financial reward, but rather a matter of good manners. Natural help or responding to requests he makes (such as helping him fix something at home, giving him a ride, etc.), when it is a reasonable and accepted assistance between friends, and especially if you would have helped even without the loan – will usually not be considered usury. If you reach a situation where it is clear to everyone that you are “enslaved” to him and are willing to do things for him that you would not dream of doing to anyone else, and he even feels that you are “compensating” him for the loan – there may be a concern about usury. Especially if there is a feeling that the benefits or help are a “hidden condition” or compensation for the profit that the lender could have made with his money instead of lending you.

When is it still worth consulting a rabbi?

If it is a help or service that is completely unusual in relation to your normal relationship – to the point that it is clear that you would have refused or would not have done it at all for others. If something was done or agreed upon (overtly or implicitly) as part of the terms of the loan (“I am lending you, on condition that you help me for the next year with my garden/business”). If you intend to give him a significant benefit beyond the customary gratitude.

Bottom line:
Thanking a friend, noting his kindness to others in a natural way, and helping him occasionally when he asks – is generally not considered usury. It is proper behavior of gratitude between people. The concern for usury in things exists mainly when there is an actual or excessive “return” for the loan, especially if it serves as a substitute or “compensation” for monetary interest. If you want to play it safe, consult a qualified rabbi and explain to him the exact nature of the help and treatment you wish to provide to your friend, and you will be able to receive calm and safe guidance.

You should have posted this answer as a talkback to the columns on AI. There is no answer to the question here.

Here is a proposed solution from the ai to the problem you raised in your answer:
You can look at the words of the Ḥidah as follows:
When the loan is still in effect (i.e., the money has not yet been repaid), there is more reason to fear that any special treatment or excessive expression of gratitude may be considered “return” for the loan — that is, “interest on things.” Once the debt is repaid, and you no longer owe him anything, expressions of gratitude or respect no longer stand in the context of “compensation for a loan.” Therefore, precisely after you have finished repaying the money, you can show him favor and acknowledge his favor in a broad way without entering into the concern of interest.

But why is there no prohibition of interest after repayment, unlike interest on money?

Interest on money (money) is an explicit halachic definition: any monetary addition to the principal that is given as a result of the loan — at the time of the loan, during it, or after it — can be considered interest.

Interest is a different matter: it is a special relationship, an expression of respect or praise, which is not necessarily worth money. As long as the debt exists, the special relationship can be interpreted as a kind of non-monetary “payment” instead of interest. But once the debt no longer exists, the gratitude and respect do not “complement” the loan or compensate for it, and therefore the fear of interest decreases.

In any case, the very fact that the law permits thanking a person after repayment helps to resolve the practical difficulty: there is no reason why a situation should arise in which you cannot do him a favor and say hello to him for the rest of your life. But of course, in any discussion concerning interest in practice, it is advisable to consult a poskim who is familiar with the laws of interest, since sometimes small details have great significance in defining the prohibition or permission.

I don't see any addition to what I wrote here. It's still not entirely clear to me what the difference is between money and interest. Even with money, the subsequent giving of the money can be interpreted as being disconnected from the loan. Perhaps in such a situation there really is room for permissibility with money as well. But I don't remember such a source, although the explanation certainly suggests that after the connection is severed and it is no longer tied to the loan, there is no interest here. But in our case, it is said that there is a connection to the loan. He does this only because the one who lent it to him. Perhaps after he returned the money, it no longer seems connected (although there is a connection within it). And perhaps such a difference is only relevant with regard to interest in the Torah (because with interest in the Torah, one does not follow what is seen). Ultimately, I still do not fully understand this difference.