Musnad Abu Ya'la al-Mawsili 108:110

Uthman ibn Abi Shaybah narrated to us, Jarir ibn Abd al-Hamid al-Dabbi narrated to us, from Sufyan al-Thawri, from Abdullah ibn Muhammad ibn Aqil, from Jabir ibn Abdullah, who said: The Messenger of Allah (peace be upon him) used to attend the gatherings of the polytheists. He said: He heard two angels behind him, and one of them was saying to his companion, "Let us go and stand behind the Messenger of Allah (peace be upon him)." He said: The other replied, "How can we stand behind him when his most recent act was touching the idols?" He said: So he never again attended the gatherings of the polytheists after that.