Musnad Ahmad 789:12

'Abd al-Rahman ibn Mahdi narrated to us, Shu'bah narrated to us, from 'Ali ibn Zayd, from al-Mughirah ibn Abi Barzah, from his father, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Aslam, may Allah keep it safe, and Ghifar, may Allah forgive it. It is not I who said it, but Allah who said it."