Amr bin Shu'ayb narrates from his father, from his grandfather (may Allah be pleased with him), that at the time of the Conquest of Makkah the Messenger of Allah (peace and blessings be upon him) said: "Allah and His Messenger have forbidden the sale of wine, carrion, pork and idols." At that time he (peace and blessings be upon him) was asked about the fat of carrion, since waterskins and hides are greased with it and people light lamps with it. He (peace and blessings be upon him) said: "Even so, it is unlawful." Then he said: "May Allah destroy the Jews! When fat was made unlawful, they melted it, sold it, and consumed its price." The Shaykh said: The impurity of carrion is heavier, whereas the impurity of oil is lighter.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19631