Bulugh al-Maram 83
Narrated Ibn ‘Abbas (rad):
Allah’s Messenger (ﷺ) said: “Satan comes to one of you in Salat and blows air in his bottom, so he imagines that he has realised air yet he did not. So if he gets that feeling he should not leave his prayer unless he hears the sound (of the air) or smells its odour.” [Reported by Al-Bazzar].
وَعَنِ اِبْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا; أَنَّ رَسُولَ اَللَّهِ ‏- صلى الله عليه وسلم ‏-قَالَ: { يَأْتِي أَحَدَكُمُ الشَّيْطَانُ فِي صَلَاتِهِ, فَيَنْفُخُ فِي مَقْعَدَتِهِ فَيُخَيَّلُ إِلَيْهِ أَنَّهُ أَحْدَثَ, وَلَمْ يُحْدِثْ, فَإِذَا وَجَدَ ذَلِكَ فَلَا يَنْصَرِفُ حَتَّى يَسْمَعَ صَوْتًا أَوْ يَجِدَ رِيحًا }  أَخْرَجَهُ اَلْبَزَّار ُ  1‏ .‏‏1 ‏- رواه البزار (281)‏.‏