A person may not say to another: “Lend me a kor of wheat and I will pay you at threshing time.” But he may say to him: “Lend me until my son comes,” [or] “until I find the key.” Hillel, however, prohibits [it]. And so Hillel used to say: A woman may not lend another a loaf until she assesses its price, for perhaps wheat will become expensive, and they will come to [a transgression of] interest.