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'Abbad b. Tamim reported from his uncle that a person made a complaint to the Prophet (ﷺ) that he entertained (doubt) as if something had happened to him which had rendered his ablution invalid. He (the Prophet) said: He should not cease (to pray) unless he hears a sound or perceives a smell (of passing wind).
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، وَمُحَمَّدُ بْنُ أَحْمَدَ بْنِ أَبِي خَلَفٍ، قَالاَ حَدَّثَنَا سُفْيَانُ، عَنِ الزُّهْرِيِّ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، وَعَبَّادِ بْنِ تَمِيمٍ، عَنْ عَمِّهِ، قَالَ شُكِيَ إِلَى النَّبِيِّ صلى الله عليه وسلم الرَّجُلُ يَجِدُ الشَّىْءَ فِي الصَّلاَةِ حَتَّى يُخَيَّلَ إِلَيْهِ فَقَالَ " لاَ يَنْفَتِلُ حَتَّى يَسْمَعَ صَوْتًا أَوْ يَجِدَ رِيحًا " .
sunnah.com