"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.'" (Using translation from Ibn Mājah 513)  

شُكِيَ إِلَى النَّبِيِّ ﷺ الرَّجُلُ يَجِدُ الشَّيْءَ فِي الصَّلَاةِ فَقَالَ «لَا يَنْصَرِفْ حَتَّى يَجِدَ رِيحًا أَوْ يُسْمَعَ صَوْتًا»