Musnad Ahmad 33:662

Hujayn and Yunus narrated to us, they said: Al-Layth ibn Sa’d narrated to us, from Abu al-Zubayr, from Jabir, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever sees me in a dream has indeed seen me, for it is not appropriate for the devil to impersonate my form." And he said: "If one of you has a dream, let him not tell people about the devil playing with him in the dream."