Sahih al-Bukhari 177
Sahih al-Bukhari · Book 4: Ablutions (Wudu') · Whosoever considers not to repeat ablution except if something is discharged or passed from exit (front or back private parts)
Narrated `Abbad bin Tamim:
حَدَّثَنَا أَبُو الْوَلِيدِ ، قَالَ حَدَّثَنَا ابْنُ عُيَيْنَةَ ، عَنِ الزُّهْرِيِّ ، عَنْ عَبَّادِ بْنِ تَمِيمٍ ، عَنْ عَمِّهِ ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " لاَ يَنْصَرِفْ حَتَّى يَسْمَعَ صَوْتًا أَوْ يَجِدَ رِيحًا " .
My uncle said: The Prophet (ﷺ) said, "One should not leave his prayer unless he hears sound or smells something."