Is it permissible to trade in foreign currencies (Forex) for profit?

Currency trading is permissible on the condition of taking possession in the session of the contract. If the currencies differ (e.g., euros for dollars), their sale is permissible on the condition of immediate receipt and delivery in the session of the contract. However, if the currencies are the same (e.g., dollars for dollars), there must be equality and taking possession in the session of the contract, based on the Prophet's (peace be upon him) saying: "Gold for gold, and silver for silver… like for like, equal for equal, hand to hand. But if these types differ, then sell as you wish, if it is hand to hand."