Is it permissible to buy a car in installments from a bank that first buys it from a showroom and then sells it to the customer with a 4% profit over 60 months, knowing that the contract between the customer and the bank is signed before the bank pays the value of the car to the showroom, and there is a penalty on the customer in case of延迟 in paying the installments?

The transaction includes an impermissible usurious condition, which is the late payment penalty. This is the forbidden usury of Jahiliyyah (pre-Islamic era). Signing the contract with the bank is permissible if it is after the car has entered into the bank's possession and guarantee. Otherwise, it is selling what one does not own, which is prohibited. To ensure the buyer's seriousness, it is sufficient to take a down payment without signing a contract for the purchase of the commodity before it enters into the bank's ownership.