Sa’if 12, Mechaber: The plaintiff claims he lent the defendant a maneh and brings one witness who testifies in his favor. The defendant admits he borrowed the money, but claims in his defense that he repaid it. Alternatively, he counterclaims that the plaintiff owes him a maneh which he now wishes to set off against the maneh he admits owing the plaintiff.
In this situation the halacha is as follows. If the witness testifies he knows the defendant did not repay the money because the same money that was lent is still in the defendant’s possession, 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.
Similarly, if the witness testifies that the maturity date of the loan has not yet arrived and that therefore, based on the legal presumption that a borrower does not prepay a loan, the loan could not have been repaid, 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.
Similarly, if before the witness testified the defendant denied he borrowed money but then, in response to the testimony of the witness, the defendant changes his plea and admits he borrowed money but now claims he repaid the loan, the defendant also falls into the category of one who is obliged by the Torah to swear but is unable to do so. He must, therefore, pay.
Rama: But where the defendant can say that he has repaid the loan or returned the claimed item without contradicting the witness, he does not fall into the category of one who is obliged by the Torah to swear but is unable to do so. He may take an oath to the effect that he has repaid the money or returned the item. He will be believed on the basis of a migo that if he wanted to lie, he could have come up with a better defense. He could have denied the loan or the deposit outright rather than admitting it and claiming he repaid it.
Ner Eyal: A defendant who is faced with one witness who testifies that he borrowed money is allowed to swear that he never borrowed any money and receive judgment in his favor. Moreover, a defendant who is faced with two witnesses who testify that he borrowed money, is allowed to swear that he repaid the money and receive judgment in his favor. This is because unless the lender stipulated otherwise, money borrowed in the presence of witnesses does not have to be repaid in the presence of witnesses.
That being the case, why, asks the Sma, is the defendant in this Sa’if 13 treated differently? Why is he denied the opportunity to swear that the testimony of the one witness against him is untrue? Why is he denied the opportunity to swear that he did in fact repay the loan? Why is he denied the opportunity to swear that the maturity date has indeed arrived? If he would only be given the opportunity to swear in each of these situations, judgment would be rendered in his favor.
The Sma answers this question by reorganizing the three cases of the Mechaber in this Sa’if 13 in the following way:
The first case: “The plaintiff claims he lent the defendant a maneh and brings one witness who testifies in his favor. The defendant admits he borrowed the money but he counterclaims that the plaintiff owes him a maneh which he now wishes to set off against the maneh he admits owing the plaintiff.” In this first case, since the defendant admits he borrowed the money and did not repay it, he is not in a position to contradict the witness. He therefore falls into the category of one who is obliged by the Torah to swear but is unable to do so. He must therefore pay.
The second case: “The plaintiff claims he lent the defendant a maneh. The defendant denies he ever borrowed money. The plaintiff then brings one witness who testifies the defendant did borrow money from the plaintiff. In response to this testimony, the defendant changes his plea and admits he borrowed money, but now claims he repaid the loan.” Since in this second case the defendant first denied the loan entirely and only admitted it when faced with one witness who testified against him, he has lost his credibility. He can, therefore, no longer be trusted with an oath. He too is in the category of one who is obliged by the Torah to swear but is unable to do so. Therefore he must pay.
The third case: “The plaintiff claims he lent the defendant a maneh and brings one witness who testifies in his favor. The defendant admits he borrowed the money but claims in his defense that he repaid it. The witness then testifies that the maturity date of the loan has not yet arrived and that therefore, based on the legal presumption that a borrower does not prepay a loan, the loan could not have been repaid. The defendant responds that he admits the maturity date has not arrived but claims that, nevertheless, he did prepay the loan.” The defendant must pay because there is a chazakah, a legal presumption against him, that a person does not prepay a loan.
As the Rema points out above in this Sa’if 13, if the defendant is not in one of the three situations described and the witness merely testifies that he borrowed money or that he had the item in question in his possession, but does not testify that he did not repay the money or did not return the item, the defendant may swear a Shevuat Heiset oath of denial that he repaid the loan or returned the item. This is based on a migo. A migo, also referred to in halachic terminology as “ma li leshaker,” means that a court believes the statement of a litigant in his own defense to be true in a situation where, if he was lying, he could have come up with a better defense. In this case, the court should believe the defendant when he says he repaid the loan or returned the item, because if he was indeed lying, he could have denied the loan or deposit outright.