Sahih Muslim Book 31, Hadith Number 5922.
Chapter : The merits of ‘Ali b. Abi Talib (Allah be pleased with him).
This hadith has been transmitted on the authority of Abu Hayyan but with this addition: “The Book of Allah contains right guidance, the light, and whoever adheres to it and holds it fast, he is upon right guidance and whosoever deviates from it goes astray.