Musnad Ahmad 789:43

Sulayman ibn Dawud narrated to us, Shu'bah informed us, from Ali ibn Zayd, who said: I heard al-Mughirah ibn Abi Barzah narrating from his father, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Ghifar, may Allah forgive it; and Aslam, may Allah grant it peace. It is not I who said it, but Allah who said it."