What are the Sharia-compliant guarantees incumbent upon Islamic banks regarding a client's promise to purchase, and is the bank entitled to obligate the client to sign guarantees?

It is permissible to deal with Islamic banks in Murabaha transactions, provided they are regulated by Sharia principles. The Islamic Fiqh Academy has issued a resolution permitting Murabaha to the one who promises to purchase, if it pertains to a commodity after it has entered the ownership of the commanded party and possession has been taken. The commanded party must bear the responsibility for damage before delivery and the consequences of returning the item due to a hidden defect. Furthermore, the conditions of sale must be met, and its impediments negated. A promise that is binding on the promisor, both religiously and legally, is permissible if it is contingent on a cause and the promised party incurs a cost, and its effect is the fulfillment of the promise or compensation for damages. Mutual promising between two parties is permissible on condition of the option (khiyar), otherwise it is not permissible because it resembles a sale and the seller must own the sold item. The bank is permitted to request a seriousness margin (hamish al-jiddiyah) from the buyer. If the buyer retracts, the bank may take from this margin what it incurred in costs for acquiring the commodity and its procedures, returning the remainder. It is not permissible for the bank to take more than the actual damage incurred. It is recommended to consult local scholars for detailed inquiries about problematic transactions.