A man who sells something that is not his

The Prophet (peace and blessings be upon him) said: "Whoever has his goods lost or stolen and then sees his goods in the possession of some person, the owner has the greater right to them, and the buyer will turn to the seller for his loss."

It is narrated from Sayyiduna Ali (may Allah be pleased with him) that a man had a garment in his possession, and another man established witnesses against him that the garment was his. Sayyiduna Ali (may Allah be pleased with him) said to him: "Hand his garment over to him, and recover your loss from the one you bought it from."
Ibn Sirin said: The judges used to rule, concerning one who sells something that is not his, that it belongs to its owner when he claims it, and this man (the seller) is held liable for its equivalent.