What is the ruling on one who buys a car in installments, then sells it to the same dealership from which he bought it, without moving or driving it?

Firstly: Installment sales are permissible, whether the deferred payment is in one lump sum or multiple installments.

Secondly: If you purchase a car, it is not permissible to sell it until you have taken possession of it and it has become fully yours, even if you have not moved it from its place.

Thirdly: If there is collusion between the dealership and the first buyer for the latter to resell it to the dealership again, this is a trick involving 'inah (a type of buy-back transaction), which is forbidden.

Fourthly: If the dealership sold the car and the buyer received it, and then the buyer sold it to you and you received it with full ownership, and then you offered it for sale to anyone, and the dealership bought it without collusion, then that is permissible and there is no harm in it.