several-fold; he then sold it for three thousand dinars. What is the ruling on this profit?

Answer: There is no objection to this increase; it is perfectly lawful. Muslims have always conducted their trade in this way: they buy goods and wait for their value to rise. They may even purchase something for personal use and, when the price climbs sharply and they see a good opportunity, sell it—despite having had no prior intention to do so. The decisive factor is that the profit must simply follow market movement; if that condition is met, there is no sin, even if the value multiplies many times over.

But if the gain were produced by exchanging that gold for other gold and taking an additional amount of gold in return, this would be forbidden. Selling gold for gold is permissible only when it is weight for equal weight and hand to hand, as established in the hadith of the Messenger of Allah—peace and blessings be upon him. Therefore, when you trade gold for gold, even if one piece is purer than the other, it is lawful only on an equal-for-equal basis.