Musnad Ahmad 30:2925

Muhammad ibn Ja'far narrated to us, he said: Shu'bah narrated to us, from Abu Husayn, he said: I heard Dhakwan, Abu Salih, narrating from Abu Hurayrah, he said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "Whoever sees me in a dream has indeed seen me, for the Shaytan cannot take my form" — Shu'bah said: Or he said: "cannot resemble me." "And whoever lies about me intentionally, let him take his seat in the Fire."