Sayyiduna Abu Hurayrah (may Allah be pleased with him) relates that the Messenger of Allah (peace and blessings be upon him) said: "Whoever, after finishing the prayer, remains sitting in his place, the angels keep supplicating for him as long as his ablution is not broken or he does not stand up. The angels make this supplication: 'Allahummaghfir lahu, Allahummarhamhu' (O Allah, forgive him; O Allah, have mercy on him)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3019