Sahih Bukhari, Volume 9, Chapter 51, Hadith No. 7222, 7223:
"Jabir bin Sumura narrated: I heard the Prophet s.a.a.w. saying: There will be 12 Khalifs (Muslim Rulers who will rule to Islamic Ummah), he then said a sentence which i did not hear. My father said: All of them (those khalifs) will be from the Quraish."
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