Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) narrates from the Messenger of Allah (peace and blessings be upon him): "A dirham for a dirham and a dinar for a dinar, equal for equal; no excess (tafadul) between them is permitted." I said to Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him): Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) saw no harm in it. Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) said: I met Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) and said to him: Tell me about what you say: have you found it in the Book of Allah or in the Sunnah of the Messenger (peace and blessings be upon him)? He said: I neither find it in the Book of Allah nor did I hear it from the Messenger of Allah (peace and blessings be upon him); but you know more about the Messenger of Allah (peace and blessings be upon him) than I do. Sayyiduna Usamah bin Zayd (may Allah be pleased with them both) informed me that the Messenger of Allah (peace and blessings be upon him) said: "Usury is only in credit (deferred) transactions."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10496