Musnad Abu Ya'la al-Mawsili 130:51

Muhammad ibn Abi Bakr narrated to us, Mubarak narrated to us, Abd al-Aziz narrated to us, from Anas, from the Prophet (peace and blessings of Allah be upon him), who said: "Indeed, the Children of Israel divided into seventy-one sects, and my nation will divide into seventy-two sects, all of which are in the Fire, except for the greatest multitude (al-sawad al-a'zam)."