Is it permissible to conduct a sale after a brother has purchased a car with his brother's money and transferred its ownership to him, with an agreement to pay its price later in installments with added profit, and then to formalize the contract after the sale is complete?

It is permissible to engage in Murabaha for the one who commands the purchase, with certain conditions. Among them is that the seller must purchase the commodity for himself and take possession of it before selling it to the buyer. It is not permissible to sell a commodity before taking possession of it. The general rule is that the seller should purchase the commodity himself or appoint an agent other than the customer. However, it is permissible to appoint the customer as an agent when there is an urgent need, and in such a case, the commodity is considered a trust in his hand. If the brother purchased the car for his principal (the questioner), then the sale from the questioner to him is valid if it took place after taking possession of it and removing it from the showroom. But if the brother had purchased it for himself, then the sale is invalid, and he must annul the sale with the showroom. The questioner should then purchase the car and take possession of it, and then sell it to his brother. If annulment is not possible, the questioner should take only the principal amount without any profit, because he is then considered a lender and the sale is invalid.