Virtues and Merits of the Prophet (pbuh) and his Companions

Bukhari :: Book 4 :: Volume 56 :: Hadith 695

Narrated Ibn Abbas:

Regarding the Verse: 'And (We) made you into Shu'ub and Qabail-- (49.13) that Shu'uib means the big Qabail (i.e. nations) while the Qabail (i.e. tribes) means the branch tribes.