It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Holy Prophet (peace and blessings of Allah be upon him) said: When any one of you offers prayer and then remains seated on his prayer mat, the angels continuously say: O Allah, forgive him. O Allah, have mercy on him, as long as he does not lose his ablution or leave from there.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 10520