Sahih al-Bukhari
Sahih al-Bukhari 177
Whosoever considers not to repeat ablution except if something is discharged or passed from exit (front or back private parts)
Arabic hadith text
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 "
Translation
Narrated `Abbad bin Tamim
My uncle said: The Prophet (ﷺ) said, "One should not leave his prayer unless he hears sound or smells something."