Musnad Ahmad 31:352

Wahb narrated to us, my father narrated to us, he said: I heard Yunus, from al-Zuhri, from Abu Salamah, from Abu Sa’id al-Khudri, from the Prophet, peace and blessings of Allah be upon him, who said: "There has not been a prophet sent, nor a successor appointed, except that he had two inner circles: an inner circle that commands him to do good and urges him toward it, and an inner circle that commands him to do evil and urges him toward it. And the protected one is he whom Allah protects."