It was narrated from Abu Hurairah (RA) that the Messenger of Allah (peace be upon him) said: “The angels send Salah upon any one of you so long as he is in the place where he prays, and so long as he does not invalidate his ablution, (saying): ‘O Allah, forgive him, O Allah, have mercy on him.'”
Sunan an-Nasa’i, Book 8, Hadith 46