It wasnarrated that Abu Hurairah said:
"The Messenger of Allah (ﷺ)usedto pray until his feet became swollen. It was said: 'O MessengerofAllah, Allah has forgiven you your past and future sins.' He said:'Should I not be a thankful slave?'" (IT)
English reference (IT): Vol. 1, Book 5, Hadith 1420 (IT)
Arabic reference (IT): Book 5, Hadith 1485 (IT)