Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) said: I came to Sayyiduna Ibn Abbas (may Allah be pleased with them both) and said: What is this that has reached (us) from you? Did you find what we did not find, or did you hear what we did not hear? (Abu Sa'id) said: I said: Then what do you say about dirhams? He said: Sayyiduna Usamah bin Zayd (may Allah be pleased with him) told us; he said: I heard the Messenger of Allah (peace and blessings be upon him) say: "There is no usury (riba) in (a transaction that is) hand to hand; usury is only in debt."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 439