The Messenger of Allah ﷺ said, "When one of you yawns during the prayer, let him suppress it as much as he can, for Shaytan enters."
قال رسول الله ﷺ: إذا تثاءب أحدكم في الصلاة فليكظم ما استطاع، فإن الشيطان يدخل.
Muslim narrated it in the Book of Asceticism and Softening of Hearts (59/2995), from Abu Bakr bin Abu Shayba, who said, Waki narrated to us, from Sufyan, from Suhayl bin Abu Salih, from the son of Abu Saeed, from his father, and he related the same account.See the remaining hadiths about yawning and blessing one who sneezes in the Book of Manners.