What is the ruling on purchasing a diamond or similar item from a bank that sells it at a price determined by the buyer, on the condition that the bank is authorized to sell it on the buyer’s behalf to reduce potential market losses, given the possibility that it might not be genuine or that the bank sells the same item to multiple individuals?

The Murabaha sale to a purchasing agent (the one who requests the purchase) goes through three stages: a promise to purchase from an individual to an institution to buy merchandise, then the institution's purchase and ownership of the merchandise, then the institution's sale of the merchandise to the agent, either in cash or installments. It is permissible for the buyer to authorize the bank to sell the commodity, but it is not permissible for the bank to buy the commodity for itself, as this would be a forbidden eenah sale (a type of buy-back transaction), nor is it permissible for the bank to oblige the buyer to sell the commodity to it.