Musnad Ahmad 1153:449

Sufyan narrated to us, from Mujalid, from al-Sha’bi, from Abu Salamah, from Aisha, who said: I saw the Messenger of Allah, peace and blessings of Allah be upon him, placing his hands on the mane of a horse while he was speaking to a man. I said: I saw you placing your hands on the mane of the horse of Dihyah al-Kalbi while you were speaking to him. He said: "And did you see [him]?" She said: Yes. He said: "That was Gabriel, peace be upon him, and he conveys peace to you." She said: And upon him be peace, and the mercy of Allah and His blessings. May Allah reward him with goodness as a companion and a guest; for he is the best of companions and the best of guests. Sufyan said: "The guest (al-dakhil) is the visitor (al-dayf)."