حَدَّثَنَا أَبُو عَمَّارٍ الْحُسَيْنُ بْنُ حُرَيْثٍ، قَالَ: حَدَّثَنَا الْفَضْلُ بْنُ مُوسَى، عَنْ مُحَمَّدِ بْنِ عَمْرٍو، عَنْ أَبِي سَلَمَةَ، عَنْ أَبِي هُرَيْرَةَ
قَالَ: كَانَ رَسُولُ اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ، يُصَلِّي حَتَّى تَرِمَ قَدَمَاهُ، قَالَ: فَقِيلَ لَهُ: أَتَفْعَلُ هَذَا وَقَدْ جَاءَكَ أَنَّ اللَّهَ تَعَالَى قَدْ غَفَرَ لَكَ مَا تَقَدَّمَ مِنْ ذَنْبِكَ وَمَا تَأَخَّرَ؟ قَالَ: أَفَلا أَكُونُ عَبْدًا شَكُورًا
“The Messenger of Allah (sallallahu alayhi wa sallam) used to perform the ritual prayer until his feet had begun to swell, so he was asked: ‘Must you do this, when it has come to you that Allah has already forgiven you your former and your latter sins?’ He replied: ‘Shall I not be a thankful servant?’”
Ash-Shama'il 253, Book 41, Worship And Devotion Of Rasoolullah, Hadith 2. 1 min read