Sa’if 13, Mechaber: The plaintiff claims the defendant owes him a maneh. The defendant responds, “You are only owed fifty dinarim and I do not know if I owe you the other fifty dinarim.”
Since the defendant is unable to swear that he does not owe the plaintiff the other fifty dinarim because he does not know, he is in the category of one who is obliged by the Torah to swear but is unable to do so. He therefore must repay the entire maneh. The plaintiff is entitled to the entire maneh without having to swear.
However, the defendant may ask the court to excommunicate the plaintiff for having taken something that in fact does not belong to him, if he is lying.
If the defendant responds that he borrowed fifty dinarim and repaid them but does not know whether he borrowed the other fifty, he must swear a Shevuat Heiset oath that he repaid the fifty and that he does not know whether he borrowed the other fifty. He will then be exempt from paying anything.
Ner Eyal: In the first case brought by the Mechaber above, if instead of saying “You are only owed fifty dinarim and I don’t know if I owe you the other fifty dinarim,” the defendant says “I don’t know if I owe you anything except for fifty dinarim,” the halacha would be different. In this second formulation, the defendant may swear the Modeh Bemiktzat oath of partial admission and is exempt from paying the other fifty dinarim.
This is because in the second formulation, the defendant did not end his admission with the words “I don’t know.” In the first formulation, however, as soon as he admits he owes fifty dinarim, he is obliged to take the Modeh Bemiktzat oath of partial admission, but he then immediately disqualifies himself from doing so when he follows by saying “I don’t know.”
In the second case brought by the Mechaber above, where the defendant responds that he borrowed fifty dinarim and repaid them but does not know whether he borrowed the other fifty, he is effectively denying the whole claim and admitting nothing. Since he now disputes the entire claim, he is like any other defendant who denies the whole claim. He is given the option of swearing the Shevuat Heiset oath of denial. If he is prepared to do so, he is entirely exempt.
