The Book on Government (Kitab Al-Imara)
Muslim :: Book 20 : Hadith 4473
It has been narrarted on the authority of Abu Huraira that the Messenger of Allah (may peace be upon him) said: People are subservient to the Quraish: the Muslims among them being subservient to the Muslims among them, and the disbelievers among the people being subservient to the disbelievers among them.