Waki' bin 'Udus narrated from Abu Razin that the Prophet (s.a.w) said:
" The Muslim's dreams are a portion of the forty-six portions of Prophet-hood. And it is (as if it is) on the leg of a bird, as long as it is not spoken of. But when it is spoken of it falls." (FR)
English reference (FR): Vol. 4, Book 8, Hadith 2279 (FR)
Arabic reference (FR): Book 34, Hadith 2448 (FR)