It is narrated from Sayyiduna Abu Juhayfah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever sees me in a dream, it is as though he has seen me while awake, for Satan cannot take my form."
Hadith Referenceالمعجم الكبير للطبراني / باب الواو / 18499