Riyad us Saliheen: Hadith 842

The Prophet (ﷺ) said, "A good vision (dream) is from Allah and a bad dream is from the Satan. He who sees something in a dream that he dislikes, should blow thrice on his left, must seek Allah's Refuge from the evil of the Satan (i.e., by saying: A'udhu billahi minash-Shaitanir-Rajim). Then it will not harm him."

[Al-Bukhari and Muslim].