Sunan an-Nasa'i, Volume 2, Book 20, Hadith 1645 (DarusSalam) ⓘ

It was narrated that Ziyad bin Ilaqah said: "I heard Al-Mughirah bin Shu'bah say: 'The Prophet stood (in prayer at night) until his feet swelled up, and it was said to him: Allah has forgiven your past and future sins. He said: "Should I not be a thankful slave?'"

أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، وَمُحَمَّدُ بْنُ مَنْصُورٍ، - وَاللَّفْظُ لَهُ - عَنْ سُفْيَانَ، عَنْ زِيَادِ بْنِ عِلاَقَةَ، قَالَ سَمِعْتُ الْمُغِيرَةَ بْنَ شُعْبَةَ، يَقُولُ قَامَ النَّبِيُّ صلى الله عليه وسلم حَتَّى تَوَرَّمَتْ قَدَمَاهُ فَقِيلَ لَهُ قَدْ غَفَرَ اللَّهُ لَكَ مَا تَقَدَّمَ مِنْ ذَنْبِكَ وَمَا تَأَخَّرَ ‏.‏ قَالَ ‏ "‏ أَفَلاَ أَكُونُ عَبْدًا شَكُورًا ‏" ‏ ‏.‏