بُلُوغُ الْمَرَامِ
Bulugh al-Maram 205
The Book of Prayer
عَنْ عَلِيِّ بْنِ طَلْقٍ - رضى الله عنه - قَالَ : قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ إِذَا فَسَا أَحَدُكُمْ فِي اَلصَّلَاةِ فَلْيَنْصَرِفْ , وَلْيَتَوَضَّأْ , وَلْيُعِدْ اَلصَّلَاةَ } رَوَاهُ اَلْخَمْسَةُ , وَصَحَّحَهُ اِبْنُ حِبَّانَ . [1]
Narrated 'Ali bin Talq (RA): Allah's Messenger (ﷺ) said: "When one of you releases air (through his anus) during Salat (prayer), he should break the Salat (prayer) then perform ablution and repeat the prayer." [Reported by al-Khamsah and Ibn Hibban graded it Sahih (authentic)].
Sunnah.com reference: Book 2, Hadith 68