Ruling on selling what one does not own and selling an item before taking possession of it

Question:
I went to a person to buy a car, so he went with me to a showroom and found its price to be twenty thousand. He said: "I will buy it for you, and you will pay me twenty-six thousand riyals for this, for a full year, with a down payment of two thousand." He bought it for me from the showroom, and I sold it at the same time for nineteen thousand and five hundred to the owners of the same showroom. Is there any riba in this?

Answer:
This requires detailed explanation. First, it must be known that it is not permissible to agree on this beforehand. Rather, the agreement and the sale must occur after the purchase. If the merchant buys it, owns it, and the car is in his possession, then he may sell it. However, selling it before that is not valid; it is invalid. But once he owns it and buys it, the sale can take place after that.
As for his saying, "Buy it for me, and I will buy it from you," this falls under the category of a promise or an agreement, but it does not constitute a purchase or a sale. Nothing is completed until the seller owns it, takes possession of it, and buys it, and then he disposes of it. Then, if you buy it from the seller, you must not dispose of it while it is still in its place. Take it to another location, to another showroom, or to your house, and then dispose of it after that.