Sahih Muslim Book 29, Hadith Number 5638.

Chapter : The saying of the Holy Prophet (may peace be upon him): He who sees me in a dream in fact sees me.

Jabir reported Allah’s Messenger (may peace be upon him) as saying: He who saw me in sleep in fact saw me, for it is not possible for the satan to appear in my form; and he also said: When any one of you sees a (hulm) he should not inform anyone, for it is a sort of vain sport of devil in the state of sleep.