Musnad Abu Ya'la al-Mawsili 159:16

Abu Khaythama narrated to us, Sufyan narrated to us, from Abu al-Zinad, from al-A'raj, from Abu Hurayrah, attributing it to the Prophet (may Allah bless him and grant him peace), who said: "The people are followers of Quraysh in this matter. Their Muslim is a follower of their Muslim, and their disbeliever is a follower of their disbeliever."