Sahih Muslim #1508 · The Book of Marriage

Sahih MuslimAbu Huraira reported Allah's Messenger
Sahih Muslim · Book 16 · The Book of Marriage
Sahih Muslim · كتاب 16 · كتاب النكاح
The angels invoke blessings on everyone among you so long as he is in a place of worship with these words: O Allah! pardon him, O Allah, have mercy upon him, (and they continue to do so) as long as, he ablution (of the worshipper) is not broken, and one among you is in prayer and so long as he is detained for the prayer.
وَحَدَّثَنَا ابْنُ أَبِي عُمَرَ، حَدَّثَنَا سُفْيَانُ، عَنْ أَيُّوبَ السَّخْتِيَانِيِّ، عَنِ ابْنِ سِيرِينَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏
"‏ إِنَّ الْمَلاَئِكَةَ تُصَلِّي عَلَى أَحَدِكُمْ مَا دَامَ فِي مَجْلِسِهِ تَقُولُ اللَّهُمَّ اغْفِرْ لَهُ اللَّهُمَّ ارْحَمْهُ مَا لَمْ يُحْدِثْ وَأَحَدُكُمْ فِي صَلاَةٍ مَا كَانَتِ الصَّلاَةُ تَحْبِسُهُ ‏"‏ ‏.‏
Reference : Sahih Muslim 1508In-book reference : Book 5, Hadith 341