For example, he sold him wheat for two hundred dirhams, payable after one year. When the year elapsed, he said, “I have nothing but dates.” So he said, “I will take the dates,” and took from him four hundred kilograms of dates worth two hundred and fifty dirhams. This is not permissible, because he has now profited from something for which he had not assumed liability. The dates are worth two hundred and fifty, whereas the man owes two hundred; thus, in exchange for two hundred, he gained two hundred and fifty from something for which he had not assumed liability. The Prophet ﷺ prohibited “profiting from that for which one has not assumed liability.”

For if this were permissible, anyone owed dirhams by another person could, when the debt fell due, say, “Give me food in place of them.” The dirhams amount to two hundred, but he says, “Give me food worth two hundred and fifty,” thereby making a profit. Then, perhaps, every time the debt falls due, he would take compensation greater than the debt, so that the profit would be repeatedly multiplied at the expense of this poor man, resulting in harm.

His statement: “Or he buys it for cash at a lower price than that for which he sold it on credit.” An example of this is that I sell Zayd a car for twenty thousand, payable after one year; this is a deferred sale. I then buy it back from that man for eighteen thousand. This is unlawful and impermissible, because he is using a stratagem: I nominally sell the car for twenty thousand, then buy it back for eighteen thousand in cash. Thus, he has received eighteen thousand from me and will repay me twenty thousand. This is usury, and it is not permissible, because it is an obvious stratagem. For this reason, Ibn Abbas, may Allah be pleased with him,