Bukhari Collection: ::Book Number 4:: Hadith # 700
Narrated Abu Huraira:The Prophet said, "The tribe of Quraish has precedence over the people in this connection (i.e the right of ruling). The Muslims follow the Muslims amongst them, and the infidels follow the infidels amongst them. People are of different natures: The best amongst them in the pre-lslamic period are the best in Islam provided they comprehend the religious knowledge. You will find that the best amongst the people in this respect (i.e. of ruling) is he who hates it (i.e. the idea of ruling) most, till he is given the pledge of allegiance."