Sahih al-Bukhari 42
Sahih al-Bukhari · Book 2: Belief · (What is said regarding the superiority of) a person who embraces Islam sincerely.
Narrated Abu Huraira:
حَدَّثَنَا إِسْحَاقُ بْنُ مَنْصُورٍ ، قَالَ حَدَّثَنَا عَبْدُ الرَّزَّاقِ ، قَالَ أَخْبَرَنَا مَعْمَرٌ ، عَنْ هَمَّامٍ ، عَنْ أَبِي هُرَيْرَةَ ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا أَحْسَنَ أَحَدُكُمْ إِسْلاَمَهُ، فَكُلُّ حَسَنَةٍ يَعْمَلُهَا تُكْتَبُ لَهُ بِعَشْرِ أَمْثَالِهَا إِلَى سَبْعِمِائَةِ ضِعْفٍ، وَكُلُّ سَيِّئَةٍ يَعْمَلُهَا تُكْتَبُ لَهُ بِمِثْلِهَا " .
Allah's Messenger (ﷺ) said, "If any one of you improve (follows strictly) his Islamic religion then his good deeds will be rewarded ten times to seven hundred times for each good deed and a bad deed will be recorded as it is."