Musnad Abu Ya'la al-Mawsili 3:107

Abu Khaythama narrated to us, Ya'qub ibn Ibrahim narrated to us, my father narrated to me, from Ibn Ishaq, and he mentioned Muhammad ibn Ka'b, from al-Harith ibn 'Abd Allah al-A'war, from 'Ali, who said: I heard the Messenger of Allah (peace and blessings of Allah be upon him) saying: "Gabriel came to me and said: 'O Muhammad, your nation will differ after you.' I said: 'Then where is the way out, O Gabriel?' He said: 'The Book of Allah. Through it, Allah breaks every tyrant, and whoever holds fast to it is saved, and whoever abandons it perishes. It is a decisive statement, not a jest. Tongues cannot distort it, it does not wear out from frequent repetition, and its wonders do not cease. In it is the news of those who were before you and the information of what is to come after you.'"