Is it obligatory to return the value of the engine to the seller after discovering its soundness, despite agreeing to bear any other defect?

The buyer is not obligated to inform the seller that the item was found to be other than what they had both thought, nor is he required to pay the value of the device's motor that he used; for the seller might have bought it defective and sold it as such, and no harm would befall him in that. Most jurists have stipulated that the sale proceeds if the seller thought the sold item was defective but then it turned out to be sound, and nothing is returned to the seller; because if the sale contract is concluded and fulfills its conditions, it entails the transfer of ownership of the item to the buyer and the price to the seller.