Ibn Abbas (may Allah be pleased with them both) narrates: I heard Sayyiduna Usamah bin Zayd (may Allah be pleased with him) say that the Messenger of Allah (peace and blessings be upon him) said: "Usury (riba) is only in debt" or he said: "in deferred payment" (the narrator is in doubt).
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 438