Narrated Abu Hurairah:
that the Messenger of Allah (ﷺ) said: "The sneeze is from Allah and the yawn is from Ash-Shaitan. So when one of you yawns let him cover his mouth with his hand. For when he says 'Ah, Ah' Ash-Shaitan laughs from inside his opening." [And indeed Allah loves the sneeze and He dislikes the Yawn, so when a man says Ah, Ah when yawning, indeed Ash-Shaitan laughs from inside his opening."] (IT)
English reference (IT): Vol. 5, Book 41, Hadith 2746 (IT)
Arabic reference (IT): Book 43, Hadith 2970 (IT)