Mu'awiyah bin Al-Hakam As-Sulami (May Allah be pleased with him) reported:
While I was in Salat with Messenger of Allah (ﷺ), a man in the congregation sneezed and I responded with: 'Yarhamuk-Allah (Allah have mercy on you).' The people stared at me with disapproving looks. So I said: "May my mother lose me. Why are you staring at me?" Thereupon, they began to strike their thighs with their hands. When I saw them urging to me to remain silent, I became angry but restrained myself. When Messenger of Allah (ﷺ) concluded his Salat. I have never before seen an instructor who gave better instruction than he, may my father and mother be sacrificed for him. He neither remonstrated me, nor beat me, nor abused me. He simply said,"It is not permissible to talk during Salat because it consists of glorifying Allah, declaring His Greatness as well as recitation of the Qur'an," or he said words to that effect." I said: "O Allah's Messenger, I have but recently accepted Islam, and Allah has favoured us with Islam. There are still some people among us who go to consult soothsayers." He said, "Do not consult them." Then I said: "There are some of us who are guided by omens." He said, "These things which come to their minds. They should not be influenced by them."(Muslim).
App reference: Book 2, Hadith 21
Arabic/English book reference: Book 2, Hadith 701