Sahih al-Bukhari 3939, 3940

It is related that Abu'l-Minhal 'Abdu'r-Rahman ibn Mut'im said, "Sharik sold me some dirhams in the market with delayed payment and I said, 'Glory be to Allah! Is this permissible?" He said, 'By Allah, I sold it in the market and no one criticised us for it. So I asked al-Bara' ibn 'Azib and he said, 'The Prophet, may Allah bless him and grant him peace, came to Madina when we were making this transaction and he said, "There is no harm if it is hand to hand. There is no harm if it is hand to hand. If there is a delay, then it is not permissible." Go and meet Zayd ibn Arqam and asked him, as he is the greatest trader of us.' So I asked Zayd ibn Arqam and he said the like of it." Once Sufyan said, "The Prophet, may Allah bless him and grant him peace, came to us Madina while we were conducting business. He said, 'On delay until the festival - or the hajj.'"