Sahih al-Bukhari 3939, 3940

Ali ibn Abdullah narrated to us: Sufyan narrated to us, from Amr, who said: I heard Abu al-Minhal Abd al-Rahman ibn Mutʿim say: “A business partner of mine sold dirhams in the market on credit. I said, ‘Glory be to Allah! Is this permissible?’ He replied, ‘Glory be to Allah! By Allah, I have sold them that way in the market, and no one objected.’ I asked al-Bara ibn Azib, and he said, ‘The Prophet (peace and blessings be upon him) came while we were trading in this way. He said, “A hand-to-hand transaction is permissible, but a deferred one is not.” Go and ask Zayd ibn Arqam, for he was the greatest trader among us.’ I asked Zayd ibn Arqam, and he said the same.” Sufyan once said: “The Prophet (peace and blessings be upon him) came to us in Medina while we were trading, and the deferred payment was until the market season or the Hajj.”