“The Lajnah Daa’imah was asked the following question,
Is it permissible to buy paper money and save it for the sake of selling it afterwards when its value increases?
There is no harm in buying any goods, keeping them for sale, and selling them when the price rises on the condition that this does not involve any disadvantage to Muslims. In accordance, if a person buys some English or Egyptian pounds, Iraqi dinars, and so on, and holds them so that when their value increases they will sell them, there is no blame on this provided that exchange is made in the same session. This may be called monopoly and it is not allowed if it involves any harm to Muslims in their food and the like.” End quote. [Reference]
AbdulFattaah Bin Uthman