Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings of Allah be upon him) said: "When any one of you sneezes, he should say 'Alhamdulillah' (All praise is due to Allah), and his (Muslim) brother or companion should say to him 'Yarhamukallah' (May Allah have mercy on you). When he says to him 'Yarhamukallah', then (the one who sneezed) should say: 'May Allah guide you and set your condition right.'" Narrated by al-Bukhari.