Sahih Muslim | Book 29 | Hadith Number 5619
Narrated by Abu Salama replied: I
Abu Salama replied: I used to see (such horrible dreams) that I fell ill. I saw Abu Qatada who also said: I used to see dreams which made me sick until I heard Allah's Messenger (may peace be upon him) as saying: Good dreams are from Allah, so if any one of you sees which he likes he should not disclose it to one but who he loves, but if he sees something which he does not like he should spit on his left side thrice and seek refuge with Allah from the mischief of the satan and its mischief (i.e. of the dream), and he should not relate it to anyone, then it would not harm him.