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)?"

The Prophet (ﷺ) used to offer prayer at night (for such a long time) that his feet used to crack. I said, "O Allah's Messenger (ﷺ)! Why do you do it since Allah has forgiven you your faults of the past and those to follow?" He said, "Shouldn't I love to be a thankful slave (of Allah)?' When he became old, he prayed while sitting, but if he wanted to perform a bowing, he would get up, recite (some other verses) and then perform the bowing.