It was narrated that Ziyad bin Ilaqah said:"I heard Al-Mughirah bin Shu'bah say: 'The Prophet (ﷺ) 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 " .
Nesai
The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day • Hadith 1644