Jabir bin Abdullah (may Allah be pleased with both of them) says that he heard the Messenger of Allah (peace and blessings of Allah be upon him) say inside Makkah in the year of the conquest of Makkah: "Allah and His Messenger have forbidden the sale of alcohol, dead animals, pigs, and idols." It was asked, "O Messenger of Allah! Tell me about the fat of dead animals; it is used to caulk ships, applied to leather, and people use it to light lamps?" He replied, "No, it is not permissible, it is forbidden." Then at that very moment he said, "May Allah curse the Jews; Allah made fat forbidden for them, so they melted it, sold it, and consumed its price." Imam Tirmidhi says:
1- The hadith of Jabir (may Allah be pleased with him) is Hasan Sahih,
2- There are also ahadith on this topic from Umar and Ibn Abbas (may Allah be pleased with them),
3- The people of knowledge act upon this.