´Al-Mughirah bin Shu'bah narrated:` "Allah's Messenger (S) performed Salat until his feet were swollen, so it was said to him: 'You burden yourself like this, while your past and future sins have been forgiven?' He said: 'Shouldn't I be a grateful worshipper?'"
Hadith Referenceسنن ترمذي / أبواب السهو / 412
Hadith Gradingالألبانی:صحيح، ابن ماجة (1419 - 1420)