Sayyiduna Usamah bin Zayd (may Allah be pleased with them both) narrates from the Prophet (peace and blessings be upon him) that the Prophet (peace and blessings be upon him) said: "Usury (riba) is in credit (deferred) transactions."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10495