Is it permissible for the first seller to buy the car from the buyer in installments, knowing that the buyer has not yet paid all the installments?

It is impermissible for someone who purchased a car in installments to sell it back to the seller for less than the purchase price, whether the sale is immediate or in installments. This falls under the forbidden transaction of 'inah (buy-back) sale. Two exceptions to this rule are: 1. When the car's condition changes in a way that reduces its market value. 2. When the buyer first pays off all outstanding installments due on the car.

If the car has been used during this period and its value has decreased, there is no harm in selling it back to the original seller at its market value. However, it is preferable to sell it to someone other than the original seller, or to settle the remaining price before selling it.