Sahih al-Bukhari 4836

Narrated Al-Mughira:

The Prophet 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)?"

حَدَّثَنَا صَدَقَةُ بْنُ الْفَضْلِ، أَخْبَرَنَا ابْنُ عُيَيْنَةَ، حَدَّثَنَا زِيَادٌ، أَنَّهُ سَمِعَ الْمُغِيرَةَ، يَقُولُ قَامَ النَّبِيُّ ﷺ حَتَّى تَوَرَّمَتْ قَدَمَاهُ فَقِيلَ لَهُ غَفَرَ اللَّهُ لَكَ مَا تَقَدَّمَ مِنْ ذَنْبِكَ وَمَا تَأَخَّرَ قَالَ " أَفَلاَ أَكُونُ عَبْدًا شَكُورًا ".