Musnad Ahmad 30:769

Mu'ammal ibn Isma'il narrated to us, Hammad ibn Salamah narrated to us, Bard ibn Sinan narrated to us, from al-Zuhri, from Abu Salamah, from Abu Hurairah, and Muhammad ibn 'Amr, from Abu Salamah, from Abu Hurairah, that the Prophet, peace and blessings of Allah be upon him, said: "There is no prophet nor successor"—or he said: "There is no prophet except that he has two inner circles (bitanatan): an inner circle that commands him to do good and forbids him from evil, and an inner circle that does not spare him from corruption. And whoever is protected from the evil of the bad inner circle has been protected"—he said it three times—"and he is with the one that prevails over him of the two."