حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا حَمَّادٌ، عَنْ ثَابِتٍ، عَنْ أَبِي رَافِعٍ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ لاَ يَزَالُ الْعَبْدُ فِي صَلاَةٍ مَا كَانَ فِي مُصَلاَّهُ يَنْتَظِرُ الصَّلاَةَ تَقُولُ الْمَلاَئِكَةُ اللَّهُمَّ اغْفِرْ لَهُ اللَّهُمَّ ارْحَمْهُ حَتَّى يَنْصَرِفَ أَوْ يُحْدِثَ ‏"‏ ‏.‏ فَقِيلَ مَا يُحْدِثُ قَالَ يَفْسُو أَوْ يَضْرِطُ ‏.‏

Abu Hurairah reported the apostle of Allah (May peace be upon him) as saying; The servant (of Allah) is considered to he at prayer so long as he remains at the place of prayer waiting for prayer. The angels say: O Allah, forgive him? O Allah, take mercy on him, until he turns away, or he is defiled. He was asked: what is meant by defilement? He replied: he breaks wind gently or loudly. Translation Not Available

Book Ref: Sunan Abi Dawud Book 2 Hadith 471
Web Ref:  Sunan Abi Dawud Book 2 Hadith 471