Currency is mainly a medium of exchange used to facilitate life and people’s transactions. Throughout history, it has taken on many forms of which gold and silver were predominant. However, for reasons that are too complicated to be mentioned here, people developed monetary institutions to issue such currency. In modern times, most of the available currencies are banknotes and coins made of other metals.
Responding to this issue, Dr. Salah As-Sawi stated,
When currency has stopped being circulating in the market or people no longer deal with it, the rules for money cease to apply and it becomes like any other form of merchandise.
Therefore, it can be sold just like any other item, for more or for less, upon the mutual satisfaction of both parties. This is so, unless it is of gold or silver, in which case it can only be sold on condition that delivery and payment occur simultaneously, according to the following saying of the Prophet (peace and blessings be upon him ) in respect to trading the six riba -related commodities (gold, silver, dates, salt, wheat and barley): “So, if these kinds differ, trade them as you like, as long as it is hand over hand (simultaneous exchange). ”