On yesterday’s daf we learned the halakha in a case where someone claims that another person owes him money. If the defendant denies it entirely we believe him without requiring him to bring any further proof; if he denies that he owes all of the money, but admits that he owes part of it – that is, if he is modeh be-miktzat – then he must pay the amount that he admits to and then take an oath that he does not owe any more.
Our Gemara introduces a case where it is not clear whether this rule applies. The baraita presents a situation where a promissory note reads that one person borrowed sela’im or dinarim – without stating the amount of sela’im or dinarim that were lent – and the lender claims that he lent five sela’im or dinarim and the borrower claims that he only borrowed three. In this case, Rabbi Shimon ben Elazar rules that we are dealing with a typical case of modeh be-miktzat; the borrower must pay what he admits to and take an oath that he does not owe the rest. Rabbi Akiva disagrees, arguing that in this case the borrower is a mashiv avedah – he is “returning a lost object (money)” by admitting what he owed.
Rabbi Akiva’s position can be explained by pointing out that the promissory note indicates that sela’im or dinarim were lent. Since they were written in the plural, we can assume that the amount that was lent was the smallest plural amount, i.e. two sela’im or dinarim. Thus, by admitting to three, the borrower is a mashiv avedah.
Of course, based on this logic, every modeh be-miktzat is a mashiv avedah since the claimant has no proof that any money is owed to him. The Rambam explains this based on Rabba’s reasoning that we saw on yesterday’s daf. Ordinarily, “En adam me’iz panav lifne ba’al hovo – we work with the assumption that a person will not have the temerity to deny his obligation to the face of the lender.” In this case, however, since the promissory note supports the borrower’s claim, we might think that he would lie to the lender. Therefore his admission is seen as being mashiv avedah.