Musnad Ahmad 32:1905

'Affan narrated to us, 'Abd al-'Aziz ibn al-Mukhtar narrated to us, Thabit narrated to us, Anas ibn Malik narrated, saying: The Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever sees me in a dream has indeed seen me, for the devil does not impersonate me. And the dream of the believer is one part of forty-six parts of prophethood." 'Affan said: So I asked Hammad, and he narrated it to me, and he went [to look] in his notes.