What is the ruling regarding the exchange of money (Sarf)?
Chapter on Riba (Usury) and Exchange (Sarf)
Al-Mughni
Book of Sales
Primary text
Sarf, which is the exchange of money (specie) for other money, requires physical exchange (qabd) between the transacting parties within the same sitting (majlis) as a mandatory condition for its validity. There is universal consensus among scholars whose opinions we know that if the parties separate before the mutual handover, the Sarf transaction is void (fasid). This is established by the hadiths concerning Riba, such as the Prophet's saying, "Gold for silver is Riba except hand to hand," and the command to exchange them "hand to hand."
Supporting text
Malik holds that walking away together to a destination for exchange is impermissible because the parties have left their initial sitting place. However, the correct view is that as long as the parties have not separated physically before the completion of the exchange, the condition is met, similar to being on a moving ship or riding a single moving animal together.