Musnad Ahmad 1081:1

'Abd al-Razzaq narrated to us, Ma'mar informed us, from al-Zuhri, 'Abd Allah ibn 'Amir ibn Rabi'ah informed me, from Harithah ibn al-Nu'man, who said: I passed by the Messenger of Allah, may Allah bless him and grant him peace, and Gabriel, peace be upon him, was with him, sitting in the seating area. I greeted him, then I passed by. When I returned and the Prophet, may Allah bless him and grant him peace, had departed, he said: "Did you see the one who was with me?" I said: "Yes." He said: "That was Gabriel, and he returned your greeting."