Sahih Bukhari Volume 005, Book 058, Hadith Number 120.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 58. Merits of the Helpers in Madina (Ansaar)
Narated By Ghailan bin Jarir : I asked Anas, "Tell me about the name 'Al-Ansar.; Did you call yourselves by it or did Allah call you by it?" He said, "Allah called us by it." We used to visit Anas (at Basra) and he used to narrate to us the virtues and deeds of the Ansar, and he used to address me or a person from the tribe of Al-Azd and say, "Your tribe did so-and-so on such-and-such a day."