It is narrated from Sayyiduna Khuzaymah bin Thabit (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "O Allah, forgive the Ansar, and the sons of the Ansar, and forgive the sons of the sons of the Ansar as well."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 3707