Buying Dollars with Saudi Riyals on Deferred Payment

Question:
A man asks about buying one thousand dollars for two thousand dollars on deferred payment, with the payment between them to be in Saudi riyals. Is this permissible?

Answer:
No, this is not permissible. In the five categories, selling currency for currency must be immediate; this is not permissible whether it is of the same type or a different type. This applies if it is deferred. If the currency is of the same type, meaning if it is deferred, or if he buys one thousand dinars, one thousand dollars, one thousand five hundred dollars, or anything else, this is only if it is received immediately. If it is deferred, if he buys one thousand dollars for fifty thousand Saudi riyals and one thousand dollars, this is riba al-nasi'ah (usury of deferment). They said it is permissible, but it is riba al-nasi'ah, but this does not matter.