Q: Can one buy and sell foreign currencies?
A: Trading in foreign exchange by buying and selling currencies is totally permissible provided at least one of the two currencies is present and take into possession at the time of the transaction. If a deal of this nature is done while none of the two commodities is present, it will not be permissible. This obviously applies to the exchange of different currencies such as rands for dollars, or dollars for riyals, and so forth.
And Allah Ta’ala knows best.
Mufti Siraj Desai