From Sahih Bukhari (Hadith 4836):
Narrated Al-Mughira:The Prophet (ﷺ) used to offer night prayers till his feet became swollen. Somebody said, to him," "Allah has forgiven you, your faults of the past and those to follow." On that, he said, "Shouldn't I be a thankful slave of Allah)?
Reference: Bukhari 4836