From Sahih Muslim (Hadith 4710):
It has been reported on the authority of Jabir b. Samura who said:I went with my father to the Messenger of Allah (may peeace be upon him) and I heard him say: This religion would continue to remain powerful and dominant until there have been twelve Caliphs. Then he added something which I couldn't catch on account of the noise of the people. I asked my father: What did he say? My father said: He has said that all of them will be from the Quraish
Reference: Muslim 4710