Musannaf Ibn Abi Shayba 13:3323

Abu Bakr narrated to us, he said: Abdullah ibn Numayr narrated to us, from al-Rabi’ ibn Sa’d, he said: I asked Abu Ja’far about a man from whom I buy food, and he gives me some of it, then he stops [delivering] the rest, and he does not find what he can give me, so he says: "Sell me from your food until I give you [what is owed]." He said: "Do not approach this; this is clear usury."