What is the ruling on trading money in Islam: is it permissible or is it considered usury (riba)?

Trade is a good earning that Islam has encouraged. The Qur’an describes it as a bounty from Allah. The Prophet, peace and blessings be upon him, was asked: "Which earning is best?" He replied: "A man's work with his hand, and every righteous transaction." This means it is free from deceit, fraud, or anything that contradicts Islamic law. However, Islam has warned against the dangers of trade, such as excessive love for this world and accumulating its wealth. Trading in paper currencies is permissible, like other forms of trade, provided that it is hand-to-hand without delay, because it is considered equivalent to gold and silver.