Kathir bin 'Abdullah bin 'Amr bin 'Awf narrated from his father:
That his grandfather said: "The Messenger of Allah said: 'May Allah have mercy on the Ansar, and the children of the Ansar, and the grandchildren of the Ansar.'" (ID)
English reference (ID): Vol. 1, Book 1, Hadith 165 (ID)
Arabic reference (ID): Book 1, Hadith 170 (ID)