'Abbad bin Tamim narrated that his paternal uncle said:
"A complaint was made to the Prophet about a man who sensed something (some doubt about his ablution) during prayer. He said: 'No (he does not have to perform ablution) unless he notices a smell or hears a sound.'"
English reference: Vol. 1, Book 1, Hadith 513
Arabic reference: Book 1, Hadith 553