Language:
كتاب الوضوء
4  
Ablutions (Wudu')
(34)
Chapter: Whosoever considers not to repeat ablution except if something is discharged or passed from exit (front or back private parts)
(34)
باب مَنْ لَمْ يَرَ الْوُضُوءَ إِلاَّ مِنَ الْمَخْرَجَيْنِ، مِنَ الْقُبُلِ وَالدُّبُرِ
Sahih al-Bukhari 176

Narrated Abu Huraira:

Allah's Messenger (ﷺ) said, "A person is considered in prayer as long as he is waiting for the prayer in the mosque as long as he does not do Hadath." A non-Arab man asked, "O Abu Huraira! What is Hadath?" I replied, "It is the passing of wind (from the anus) (that is one of the types of Hadath).

حَدَّثَنَا آدَمُ بْنُ أَبِي إِيَاسٍ، قَالَ حَدَّثَنَا ابْنُ أَبِي ذِئْبٍ، عَنْ سَعِيدٍ الْمَقْبُرِيِّ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏ "‏ لاَ يَزَالُ الْعَبْدُ فِي صَلاَةٍ مَا كَانَ فِي الْمَسْجِدِ يَنْتَظِرُ الصَّلاَةَ، مَا لَمْ يُحْدِثْ ‏"‏‏.‏ فَقَالَ رَجُلٌ أَعْجَمِيٌّ مَا الْحَدَثُ يَا أَبَا هُرَيْرَةَ قَالَ الصَّوْتُ‏.‏ يَعْنِي الضَّرْطَةَ‏.‏
Reference : Sahih al-Bukhari 176
In-book reference : Book 4, Hadith 42
USC-MSA web (English) reference : Vol. 1, Book 4, Hadith 176
  (deprecated numbering scheme)