Dream

Sahih Bukhari, Volume 9, Book 87, Number 169: 

Narrated Abu Sa'id Al-Khudri:

I heard Allah's Apostle (sallAllahu 'alayhi wa salam) saying, "If anyone of you saw a dream which he liked, then that was from Allah, and he should thank Allah for it and tell it to others; but if he saw something else, i.e, a dream which he did not like, then that is from Satan and he should seek refuge with Allah from it and should not tell it to anybody for it will not harm him."