Sahih Muslim | Book 29 | Hadith Number 5618

Narrated by Abu Qatada
Abu Qatada reported Allah's Messenger (may peace be upon him) as saying: The good vision are from Allah and the evil dreams are from the satan. If one sees a dream which one does not like, one should spit on one's left side and seek the refuge of Allah from the satan; it will not do one any harm, and one should not disclose it to anyone and if one sees a good vision one should feel pleased but should not disclose it to anyone but whom one loves.