The Book of Prayers (Kitab Al-Salat)

Muslim :: Book 4 : Hadith 1396

Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: 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.