Can a merchant offer to give a discount to someone who is willing to pay in full for his purchase?
While this seems like a straightforward situation of a worthwhile business transaction – the merchant is interested in having money “in hand” and is willing to lower his profit margin in order to receive that money “up front” – the laws of ribit, of the prohibition limiting people from taking interest, limit some of these agreements.
Rav Nahman teaches a basic principle of ribit – any payment that is made whose purpose is to delay the lender from collecting his money now is considered ribit. Thus, Rav Nahman rules that if the market price for wax is fours loaves of wax for a zuz and someone selling wax offers five loaves of wax for a zuz to a purchaser who is willing to pay well before receiving the merchandise, there may be problems with the agreement. If the wax merchant has the merchandise in his possession at the time of the agreed upon sale, the agreement is valid, since the merchant is simply giving a discount in exchange for pre-payment. If, however, the wax merchant did not have an inventory of wax, he is effectively borrowing money from the purchaser, and in exchange is repaying him with more wax than was paid for – which is considered a case of paying interest on the loan. The Gemara explains that this is true even in a case where the merchant has a line of credit and will be able to get hold of the wax, nevertheless, if he does not have it in hand, we will apply Rav Nahman’s rule.
The rishonim ask why Rav Nahman needs to teach that “any payment that is made whose purpose is to delay the lender from collecting his money now is considered ribit,” which is, effectively a simple restatement of the biblical rule forbidding interest. The Ra’avad suggests that Rav Nahman’s statement is only really necessary to teach the rule as is illustrated by the case that is brought – that even in the context of a business transaction, the rule of ribit would still apply.