It was narrated from ‘Abdur Rahman bin Abi Bakrah that his father said: “The Messenger of Allah صلی اللہ علیہ وآلہ وسلم forbade us from selling silver for silver unless it was of equal amounts, or selling gold for gold unless it was of equal amounts. The Messenger of Allah صلی اللہ علیہ وآلہ وسلم said: ‘Sell gold for silver however you want, and silver for gold however you want.” (Sahih)