Answer
It is permissible to buy and sell foreign currencies.
Dealing (purchasing and selling) in foreign currency is termed as
Bay-us-Sarf. The Fuqahaa (jurists) have ruled that Tamaasul (equality) is
not necessary in the buying and selling of foreign exchange. Hence, one
dollar may be sold more than its equivalent value in rands. However,
Ittihaad-e-Majlis (one sitting) is necessary in such a transaction.
Therefore, the exchange of the dollar and rand must take place in the same
sitting. If the foreign exchange is done in different sittings as is the
case in forex companies, then the contemporary Fuqahaa have ruled that the
spot trading is sufficient to fulfil the condition of Ittihaad-e-Majlis.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai