What is the ruling on a person purchasing a commodity for an immediate price at the request of another person, then selling it to him in installments with an increase in price, knowing that the first person does not own a shop and does not buy the commodity except at the buyer's request? And is this considered a real purchase or not?

"Murabaha to the one who promises to buy" is permissible according to the majority of contemporary scholars, but on condition that the one who promises to buy is not obligated to fulfill his promise if he has a valid excuse. Otherwise, he must either fulfill the promise or compensate for the damage. However, if the one who promises to buy is obligated in all circumstances, then this is not permissible, because it is considered selling what the seller does not own at the time of the promise. The purchase that occurs between the one commissioned to buy and the owner of the commodity is valid as long as the responsibility for ensuring against damage rests with the commissioned party before delivery to the one who promised to buy, and the conditions of sale are met and its impediments are absent.