By Horav Yosef Yeshaya Braun, member of the Badatz of Crown Heights
A principle of halachic transactions is g’miras daas (firm resolve), which is achieved through a kinyan (act of acquisition), a formalized, proprietary act transferring ownership—for example, a physical object exchanges hands between two parties—to “seal the deal.” However, when a creditor wishes to be mochel (forgive) a debt, his decision to do so suffices. There is no need for a kinyan, and he may be mochel shelo b’fanav (not before him), i.e., the loan can be forgiven even without the debtor being present.
There is a discussion among poskim whether a lender can be mochel b’lev (in their heart, i.e. non-verbally) or whether the intention to forgive must be declared verbally. What happens, then, in a case where a creditor intended to pardon the debt, but before he had a chance to inform the debtor, the money was paid back? May he keep it or must he return it?
Halachah speaks of a dispute over an object where one party is a muchzak (the presumed owner based on possession). In these particular circumstances, there is a minority opinion which states that the object belongs to the muchzak. Though we usually follow the majority, in this case the strength of de facto possession allows him to proclaim, “Kim li!” (I am of that [minority] opinion)—and the object is his. The same applies for a lender who was only mochel b’lev before the debtor paid up; since there are poskim who deem non-verbal dissolution as not binding, the lender may utilize the principle of kim li and keep the repaid loan.
A creditor who is mochel cannot retract the pardon. Even if the retraction occurs toch k’dei dibbur (within the short span of a salutation, specifically, “Shalom alecha Rebbi!”—Greetings to you, Rabbi), according to some opinions, the pardon is binding—unless, of course, it was a mechilah b’taus (a pardon made in error).
Similarly, a person who volunteers services or goods at no charge for the sake of doing a mitzvah, cannot backtrack and ask for payment.