Is buying a car in installments from banks for 20,000 dinars, while its price outside the bank is 15,000 dinars, permissible or forbidden?

If banks own the cars before selling them to the customer, there is no harm in purchasing them from them through murabaha, even if the deferred sale price is higher than the immediate sale price. There is no Shariah limit for maximum profit, and the determining factor is what both parties agree upon. The mere fact that the bank's price is higher than the market price does not make the transaction unlawful, but the most important condition is that the bank genuinely owns the car before selling it. There is also no harm in selling a car purchased from the bank at a lower price in the market.