حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، وَبِشْرُ بْنُ مُعَاذٍ، قَالا‏:‏ حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ زِيَادِ بْنِ عِلاقَةَ، عَنِ الْمُغِيرَةِ بْنِ شُعْبَةَ، قَالَ‏:‏ صَلَّى رَسُولُ اللهِ صلى الله عليه وسلم، حَتَّى انْتَفَخَتْ قَدَمَاهُ، فَقِيلَ لَهُ‏:‏ أَتَتَكَلَّفُ هَذَا، وَقَدْ غَفَرَ اللَّهُ لَكَ مَا تَقَدَّمَ مِنْ ذَنْبِكَ وَمَا تَأَخَّرَ‏؟‏ قَالَ‏:‏ أَفَلا أَكُونُ عَبْدًا شَكُورًا‏.‏

It is also reported from Abu Huraira, may Allah be well pleased with him that

Allah’s Messenger (Allah bless him and give him peace) used to stand performing the ritual prayer until his feet had begun to swell, so he would be asked: “O Messenger of Allah, must you do this, when Allah has already forgiven you your former and your latter sins?” He replied: “Shall I not be a thankful servant?”