Ruling on selling one currency for another currency with a deferred payment

Question:
I have a bank account held as a trust in US dollars. Is it permissible for me to sell them for riyals for a period of six months at a price higher than their current value?

Answer:
You may not sell one currency for another except hand-to-hand, whether it is dollars or anything else, whether it is dinars and dirhams, or dollars, or otherwise, or pounds. You may not sell them except hand-to-hand. So if you have dollars, you may not sell them except hand-to-hand, whether it is Saudi riyals, or dinars, or the British pound, or the Egyptian pound, or anything else. You may not sell except hand-to-hand, and there must not be any absent currency exchanged for present currency, just as with gold and silver. These have taken their place; therefore, they may not be sold except hand-to-hand.