Is it permissible to buy a commodity (gold or a car) and sell it in installments to a financing applicant, with the condition that it be resold to the seller or to another party?

It is permissible for the buyer to purchase the commodity by installments at a price higher than its current price, and it is permissible for him to sell it for cash at a lower price than what he bought it for, provided that the buyer in this case is someone other than the original seller. This is called "mas'alat al-tawarruq" (monetization). As for selling the commodity back to the original seller for cash at a lower price than its original price, this is "bay' al-'inah" (buy-back sale), which is prohibited by the majority of scholars.