Musnad Abu Ya'la al-Mawsili 115:191

Muhammad narrated to us, Abd al-Razzaq narrated to us, Ma'mar informed us, from Qatadah, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "O Allah, forgive the Ansar, and the children of the Ansar, and the children of the children of the Ansar." And Ma'mar said, from the son of Abdullah ibn Abi Bakr ibn Amr ibn Hazm, who said: My father used to say, "There remains no one from the people of the supplication except me."