Sahih Bukhari Volume 7, Book 62, Hadith Number 21.

Narrated By Abu Huraira : The Prophet said: Abraham did not tell lies except three. (One of them was) when Abraham passed by a tyrant and (his wife) Sara was accompanying him (Abu Huraira then mentioned the whole narration and said:) (The tyrant) gave her Hajar. Sara said, “Allah saved me from the hands of the Kafir (i.e. infidel) and gave me Hajar to serve me.” (Abu Huraira added:) That (Hajar) is your mother, O Banu Ma’-As-Sama’ (i.e., the Arabs).