Is buying a car from a company in installments, then selling it to benefit from its price, considered unlawful, especially given the absence of proof of receiving the car upon paying the first installment, and the buyer not fully owning the car at the time of sale?

We understand that your friend intends to buy a car in installments from his company with the intention of selling it to benefit from its price. This is called Tawarruq (monetization). The majority of scholars permit it, and this is the most preponderant view according to us, due to the generality of the verse, "And Allah has permitted trade," and because there is no apparent intention of usury (riba) nor its form. Tawarruq is disliked by some and forbidden by others. Your friend must adhere to the Shariah regulations for installment purchases. If he takes possession of the car and receives it, he is permitted to sell it for an immediate cash price before paying the remaining installments. However, if he has not received it, or if the company does not transfer ownership until all installments are paid, then it is not permissible to sell it, because this condition is invalid as it contradicts the essence of the contract. As for pawning the car and prohibiting its sale until the full price is paid, there is no objection to this, and it must be adhered to.