Musnad Abu Ya'la al-Mawsili 117:147

Suwayd ibn Sa'id narrated to us, Zakariyya ibn Yahya al-Dhirā' narrated to us, from Thābit al-Bunānī, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) used to say: "O Allah, indeed the true life is the life of the Hereafter, so forgive the Ansar and the Muhajirun."