It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that he (peace and blessings be upon him) said: "The angels keep supplicating for mercy for any one of you as long as he remains sitting in the place where he prayed. The angels say: 'Allahummaghfir lahu, Allahummarhamhu' (O Allah, forgive him; O Allah, have mercy on him), as long as he does not lose his ablution."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3020