What is the ruling on installment transactions using customs cards for new cars that have not left the showroom, where they are purchased at a higher price, then sold on installment at a higher price to a third party who sells them back to the showroom at a lower price to obtain cash, with the showroom's prior knowledge of this?

The described transaction involves three issues:

1. First Issue: The ruling on selling cars with a customs card without physical possession: If the card accurately describes the car, then taking possession of the card is considered taking possession of the car by takhliyah (vacating the premises), and it is permissible to buy and sell it. 2. Second Issue: The ruling on selling the car after taking possession of the card: It is permissible for the first buyer to sell it to the second, either for cash or on credit, at a higher price. It is also permissible for the second buyer to sell it to the third in the same manner after taking possession of the card. 3. Third Issue: Selling the cards back to the first seller at a lower price: There is no prohibition in this, as it falls under the permissible 'eina (buy-back) transaction. This is because the prohibited aspect of 'eina is a loan that yields a benefit, which is not present here, as the first seller sold the cars for cash at a lower price than what he bought them for.