Baba Metzia 5:9-10

Baba Metzia 5:9

One person may not tell another to lend him a kor of wheat to be repaid at threshing time (because the price may increase, as explained in Mishna 5:8), but he may set such terms as “until my son returns” or “until I find my key” (i.e., when he has wheat on hand but cannot access it), though Hillel prohibits these as well. Hillel used to say that one woman may not lend a loaf of bread to another until they determine the value of the loaf. This is out of concern that the price of wheat may rise and it will become an interest-bearing transaction.

Baba Metzia 5:10

One person may propose to another, "Weed with me and I’ll weed with you" or "hoe with me and I’ll hoe with you" but he may not propose, "Weed with me and I’ll hoe with you" or vice versa. (These have different labor intensities so the discrepancy in the transaction resembles interest.) All the days of the dry season have the same status and all the days of the rainy season have the same status. Therefore, one may not propose, "Plow with me in the dry season (which is relatively easy) and I will plow with you in the rainy season (which is much harder),” (again because of the discrepancy in the intensity of labor). Rabban Gamliel says that some forms of interest are paid in advance and others are paid later, as follows: if one person wanted to borrow money from another, so he sent him a gift as an incentive to lend to him, it is interest in advance. If one person borrowed money from another and repaid it, and sent a gift to compensate the lender the time his money was unavailable for his use, it is interest paid later. Rabbi Shimon says that even words can constitute interest. Therefore the borrower must not provide the lender with useful information (that he would not otherwise have provided).