Sa’if 12, Mechaber: The plaintiff sues the defendant for the repayment of a maneh he claims he lent him. The defendant responds that he does not know whether the plaintiff lent him the money. Alternatively, he admits that he borrowed the money, but he says that he does not know if he paid it back. One witness testifies that the plaintiff lent the defendant the money in question. The defendant is now in a situation in which on the one hand he is obliged to take an oath to deny the testimony of the one witness, but on the other hand he is unable to do so because he does not know. In this situation, the defendant falls into the category of one who is obliged by the Torah to swear but is unable to do so. He must therefore pay.
Ner Eyal: Although the testimony of one witness in favor of the plaintiff is insufficient to enter a judgment against the defendant, it is sufficient to require the defendant to swear a Torah oath in rebuttal that such testimony is untrue. If the defendant so swears, judgment is entered in his favor and the testimony of the one witness is ignored.
In the case in question, however, the defendant is unable to swear, because he says he does not know whether he borrowed the money or he says he did borrow the money but does not know if he paid it back. The rule is mitoch she’eino yachol lishava, meshalem – one who cannot swear must pay. That means a person who is obliged to swear but is unable to do so must pay the full amount of the claim.
Although we have previously seen in Choshen Mishpat 75:9 that a defendant who responds that he does not know whether he owes money or not is not liable to pay anything to the plaintiff, provided he swears a Shevuat Heiset oath that he is telling the truth and indeed does not know, the situation in this case is different. Here, there is one witness supporting the plaintiff’s claim. Even though the witness only testifies to the giving of the loan and does not testify that the loan was never paid back, nevertheless his testimony does corroborate the plaintiff’s claim. The Torah believes the testimony of one witness that the defendant does not deny under oath – as if it were the testimony of two witnesses. Accordingly, weighing against the defendant in this situation is the unrefuted testimony of one witness, the certainty of the plaintiff, and the uncertainty of the defendant. The combined result of all this is a judgment against the defendant.
The Tur uses different language to describe the situation. Instead of saying that one witness testifies that the plaintiff lent the defendant the money in question, as the Mechaber does, the Tur’s formulation is “one witness testifies that the defendant owes the plaintiff money.” As suggested by the Beit Yosef, the Tur seems to adopt the explanation of the Magid Mishneh that in addition to testifying that the plaintiff lent money to the defendant, the witness also testifies that the money is still in the defendant’s possession or that the maturity date of the loan has not yet arrived. Therefore it can be assumed that the loan has not been repaid either because it was seen still to be in the defendants possession or because the maturity date has not arrived. There is a chazakah, a legal presumption, that a borrower does not repay a loan before its maturity date.
All of this, of course, fortifies the testimony against the defendant and helps to further differentiate this case from the case in Sa’if 75:9.