Musnad Ahmad 25:988

Abu Kamil and ‘Affan narrated to us—the meaning is the same—they said: Hammad narrated to us, ‘Ammar ibn Abi ‘Ammar informed us, from Ibn ‘Abbas, who said: I was with my father at the Prophet’s (peace be upon him), and there was a man with him speaking to him in private—‘Affan said: And he [the Prophet] was as if he were turning away from al-‘Abbas. So we left his presence, and he [al-‘Abbas] said: Did you not see your cousin as if he were turning away from me? I said: Indeed, there was a man with him speaking to him in private. ‘Affan said: He said: Was there someone with him? I said: Yes. He said: So he returned to him and said: O Messenger of Allah, was there someone with you? For ‘Abdullah informed me that there was a man with you speaking to you in private. He said: "Did you see him, O ‘Abdullah?" He said: Yes. He said: "That was Jibril, and he is the one who occupied me from you." ‘Affan narrated to us: That there was a man with you speaking to you in private.