Narrated Abu Hurairah:
that the Messenger of Allah (ﷺ) said: "Indeed Allah loves sneezing and He dislikes the yawn. So when one of you sneezes and says 'Al-Hamdulillah (All praise is due to Allah),' then it is a right due from every one who hears him to say: 'Yarhamukallah (May Allah have mercy upon you)' As for yawning then when one of you yawns let him suppress it as much as possible and not say: "Hah Hah' for that is only from Ash-Shaitan laughing at him." (DE)
English reference (DE): Vol. 5, Book 41, Hadith 2747 (DE)
Arabic reference (DE): Book 43, Hadith 2971 (DE)