It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: When any one of you sees a dream that he does not like, he should spit lightly to his left three times and recite "A'udhu billah" three times, and change the side on which he was lying.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 14780