Volume 4 · Book 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.
— Sahih Bukhari, Volume 4, Book 56: Virtues and Merits of the Prophet (pbuh) and his Companions, Hadith #695