It is narrated from Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) that he made a deal with Sayyiduna Talhah bin Ubaydullah (may Allah be pleased with him), selling him a hundred dinars for silver. Sayyiduna Umar (may Allah be pleased with him) demanded payment in hand (on the spot), (upon which Sayyiduna Talhah, may Allah be pleased with him) said: I have no money at the moment until my agent comes back from al-Ghabah. Sayyiduna Umar (may Allah be pleased with him) refused (to accept this) and said: No, never; I heard the Messenger of Allah (peace and blessings be upon him) say: "Trading gold for silver is usury (riba) except hand to hand (that is, cash for cash, on the spot)."
Hadith Referenceمسند أبي يعلى الموصلي / مسند عمر بن الخطاب رضي الله عنه / 209
Hadith Takhrij«قال سعيد بن محمد السناري: صحيح» «أخرجه أبو الأزرقي في "أخبار مكة" [2/ 151/ طبعة دار الأندلس]، وابن الأثير في أسد الغابة [1/ 686، مسند ابویعلیٰ ترقیم الاثری: 204»