Hadith 598
Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) said: “Indeed, Allah Almighty likes sneezing and dislikes yawning. So when someone feels like yawning, he should try his best to restrain it and should not say ‘Haa’, because when he says ‘Haa’, the devil laughs at him. And when someone sneezes, he should say ‘Alhamdulillah’, and whoever hears him praising Allah, it is obligatory upon him to say ‘Yarhamukallah’ to him.”
Imam Ibn Hibban (may Allah have mercy on him) says: I have not heard the word ‘obligatory’ (حق) in the wording of this narration from the narrator named Muhammad bin Ishaq; this statement has been mentioned by the Sheikh.