It is narrated from Sayyiduna Abu Razin (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "The dream of a believer is one of forty parts of prophethood. It is on the foot of a bird as long as it is not related; once it is related, it comes to pass."
Hadith Referenceالمعجم الكبير للطبراني / باب اللام / 16511