Shevuos 6:7-7:1

Shevuos 6:7

Let’s say that one person lends money to another based on collateral, which was subsequently lost (by the lender). The lender says, “I lent you a sela and the collateral was worth a shekel” (a shekel is half a sela, so the lender claims that the borrower still owes him the balance of a shekel). The borrower replies, “No, you lent me a sela and the collateral was worth a sela” (so the debt should be canceled). In such a case, the borrower is exempt from taking an oath (because he denies having any debt whatsoever). If the lender says, “I lent you a sela and the collateral was worth a shekel,” to which the borrower replies, “No, you lent me a sela and the collateral was worth three dinar (i.e., three-quarters of the loan), then he is liable to take an oath (because he admits to part of the debt). If the borrower says, “You lent me a sela and the collateral was worth two sela” (so the lender owes him change) and the lender replies, “No, I lent you a sela and the collateral was worth a sela,” the lender is exempt from taking an oath (because he denies the claim altogether). If the borrower says, “You lent me a sela and the collateral was worth two sela,” and the lender replies, “No, I lent you a sela and the collateral was five dinar” (which is one dinar more than a sela), then he is liable to an oath (because he admits to part of the claim). When they both have to take an oath (the borrower that he doesn't owe as much money as is claimed and the lender that he no longer has the collateral), the one who was in possession of the collateral (i.e., the lender) goes first. This is out of concern that if the borrower were to go first, the lender might produce the collateral after the borrower takes his oath.

Shevuos 7:1

All those who take Biblically-imposed oaths do so in lieu of having to pay the debt being claimed from them. The following are rabbinic oaths that were instituted to allow claimants to collect: a hired worker, a person who was robbed or injured, one whose opponent in a court case is suspected of swearing falsely, and a shopkeeper who has his records. Accordingly, if a hired worker asks his employer to pay his wages and the employer replies that he has already done so, the worker takes an oath and is paid. Rabbi Yehuda says that this is so only if the employer admits to part of the claim, e.g. the worker asks to receive his wage of 50 (silver) dinar and the employer replies that he has already repaid him a gold dinar (which is worth 25 silver dinar).