Sahih Muslim
The Book of Mosques and Places of Prayer — Hadith #1403
Scholarly Consensus: Sahih How we grade
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 " .
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.
Chain of Narration (Isnad)
Hadith Grading
Each grade below reflects one scholar's assessment of the chain of transmission. The grade describes the chain, not the Prophet's words. How we grade
Scholarly Consensus: Sahih