Sayyiduna Mu'awiyah bin al-Hakam al-Sulami (may Allah be pleased with him) said: I was with the Prophet (peace and blessings be upon him) (in prayer) when a man among the people sneezed, and I said: "Yarhamuk Allah (May Allah have mercy on you)." At this the people began to stare at me. I said: "Alas for the grief of my mother! Why are you looking at me?" The narrator said: The people began striking their thighs with their hands. When I saw that they were trying to make me quiet, I fell silent. Then, when the Messenger of Allah (peace and blessings be upon him) finished the prayer, may my father and mother be sacrificed for him, I have never seen a teacher before him or after him who taught better than he did. By Allah, he did not strike me, nor scold me, nor revile me; rather he said: "This prayer of ours is such that nothing of people's ordinary speech is proper in it; it is only glorification (tasbih), magnification (takbir) and the recitation of the Qur'an."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16994