Riyad as-Salihin

Jabir (May Allah be pleased with him) reported: Messenger of Allah (ﷺ) said, "When one of you sees a bad dream let him blow three times on his left, seek refuge in Allah from the Satan three times (i.e., by saying: A'udhu billahi minash-Shaitanir-Rajim) and change the side on which he was lying."

[Muslim].