Musannaf Ibn Abi Shayba 27:845

Yazid ibn Harun narrated to us, he said: Ibn Ishaq informed us, from Imran ibn Abi Anas, from Hanzala ibn Ali al-Aslami, from Khaffaf ibn Ima ibn Rahda al-Ghifari, who said: The Messenger of Allah (ﷺ) led us in prayer. When he raised his head from the final rak'ah, he said: "May Allah grant peace to Aslam, and may Allah forgive Ghifar." Then he turned and said: "It is not I who said this, but Allah said it."