Full Sharh — Mishkat al-Masabih 2270
وَعَنْ أَبِي سَعِيدٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: " إِذَا أَسْلَمَ الْعَبْدُ فَحَسُنَ إِسْلَامُهُ يُكَفِّرُ اللَّهُ عَنْهُ كُلَّ سَيِّئَةٍ كَانَ زَلَفَهَا وَكَانَ بَعْدَ الْقِصَاصِ: الْحَسَنَةُ بِعَشْرِ أَمْثَالِهَا إِلَى سَبْعِمِائَةِ ضِعْفٍ إِلَى أَضْعَافٍ كَثِيرَةٍ وَالسَّيِّئَةُ بِمِثْلِهَا إِلَّا أَنْ يَتَجَاوَزَ اللَّهُ عَنْهَا ". رَوَاهُ البُخَارِيّ
English Translation
Abu Sa'id reported God’s messenger as saying, “When a man accepts Islam sincerely God removes from him every sin he has previously committed. After that there will be requital, a good deed getting ten to seven hundred times as much and many times more, and an evil deed getting a punishment equivalent to it, unless God overlooks it.” Bukhari transmitted it.
Source
Mishkat al-Masabih(مشكاة المصابيح)
Supplications
Hadith Number
2270