The Book on Government (Kitab Al-Imara)
Muslim :: Book 20 : Hadith 4477
It has been narrated on the authority of Jabir b. Samura who said: I joined the company of the Holy Prophet (may peace be upon him) with my father and I heard him say: This Caliphate will not end until there have been twelve Caliphs among them. The narrator said: Then he (the Holy Prophet) said something that I could not follow. I said to my father: What did he say? He said: He has said: All of them will be from the Quraish.