I heard Allah's Messenger (ﷺ) saying in the year of the Conquest, while he was in Makkah, "Allah and His Messenger have forbidden the sale of intoxicants, dead animals, swine and idols." He was asked, "O Allah's Messenger, what about the fat of a dead animal, for it is used for greasing ships, greasing the hides (of animals), and making oils for lamps?" He replied, "No, it is unlawful." Allah's Messenger (ﷺ) then added: "May Allah curse the Jews, when Allah the Most High declared the fat of such animals unlawful they melted it, then sold it and devoured its price (profit)." [Agreed upon].

I heard Allah's Messenger (ﷺ) saying, "When two people who are arranging a business transaction disagree and there is no proof to arbitrate between them, the seller's word is final, or they may break the deal." [Reported by al-Khamsa and authenticated by al-Hakim].