Sayyiduna Muawiyah bin Hakam Sulami (may Allah be pleased with him) said: I was performing prayer with the Messenger of Allah (peace and blessings of Allah be upon him) when suddenly a man sneezed, so I said «يرحمك الله». The people began to stare at me, so I said (anxiously cursing myself), "May your mother lose you, what is the matter that you are staring at me?" When I said this, the people started striking their thighs with their hands to make me quiet. When I saw that they wanted me to be silent, I asked, "Why are you making me silent?" Then I became quiet. And when the Messenger of Allah (peace and blessings of Allah be upon him) finished the prayer, may my parents be sacrificed for you, I have never seen a better teacher before or after you. By Allah, he neither hit me, nor scolded me, nor spoke harshly to me. He only said: "This prayer of ours, it is not right to speak in it. It is only for glorification, magnification, and recitation."
Hadith Referenceسنن دارمي / من كتاب الصللاة / 1541