What is the ruling on buying mobile credit cards or dollars on credit from a bank for the purpose of selling them and buying a car, using a Murabaha system with a five-year repayment period?

Selling prepaid top-up cards is permissible. It is also permissible to sell them for more than their face value or on credit. There is no objection to conducting a tawarruq contract with them. As for buying dollars and other currencies, this is considered a currency exchange (sarf), and it requires immediate mutual possession (al-taqabud fil-hal). It is not permissible to postpone the possession of either currency, based on the saying of the Messenger of Allah, peace and blessings be upon him: "Gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, and salt for salt – like for like, equal for equal, hand to hand. If these types differ, then sell as you wish, provided it is hand to hand."