Mukhtasar Bukhari (Abridged) 1029 — Selling gold for gold

Narrated Abu Bakr (may Allah be pleased with him): The Messenger of Allah (peace and blessings of Allah be upon him) said: "Do not sell gold for gold except equal in weight (i.e., give as much gold as you take back), and (similarly) do not sell silver for silver except equal in weight. But you may buy and sell gold for silver and silver for gold as you wish."