Abu Salama reported: I used to see dreams (and was so much perturbed) that I began to quiver and have temperature, but did not cover myself with a mantle. I met Abu Qatada and made a mention of that to the him. He said: I heard Hazrat Muhammad (SAW) saying: A good vision comes from Allah and a (bad) dream (hulm) from devil. So when one of. you sees a bad dream (hulm) which he does not like, he should spit on his left side thrice and seek refuge with Allah from its evil; then it will not harm him.
Sahih Muslim Vol 5, Hadith No. 5613