The Messenger of Allah ﷺ said, "Do not sell gold for gold except in equal measure, and do not allow one portion to exceed the other. Do not sell silver for silver except in equal measure, and do not allow one portion to exceed the other. And do not sell any of it on deferred terms in exchange for what is delivered on the spot."
أن رسول الله ﷺ قال: لا تبيعوا الذهب بالذهب إلا مثلا بمثل، ولا تشفوا بعضها على بعض، ولا تبيعوا الورق بالورق إلا مثلا بمثل، ولا تشفوا بعضها على بعض، ولا تبيعوا منها شيئا غائبا بناجز.
Malik narrated it in the Book of Sales (30), from Nafi, from Abu Saeed, in like manner. Bukhari narrated it in the Book of Sales (2177), and Muslim in the Book of Musaqah (1584:75), both of them through the route of Malik, in the same manner. Muslim also narrated it through another route from Nafi, in the same manner, adding, "except hand to hand."His saying, "and do not favor one over the other," means do not give more, it is a form four verb from ashaffa, and shaff, with a kasrah, means increase, though it is also used to mean decrease.