Sahih Al Bukhari 1: Chapter 2, Hadith 42

(42) (What is said regarding the superiority of) a person who embraces Islam sincerely.

حَدَّثَنَا إِسْحَاقُ بْنُ مَنْصُورٍ، ‏‏‏‏‏‏قَالَ:‏‏‏‏ حَدَّثَنَا عَبْدُ الرَّزَّاقِ، ‏‏‏‏‏‏قَالَ:‏‏‏‏ أَخْبَرَنَا مَعْمَرٌ، ‏‏‏‏‏‏عَنْ هَمَّام، ‏‏‏‏‏‏عَنْ أَبِي هُرَيْرَةَ، ‏‏‏‏‏‏قَالَ:‏‏‏‏ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ:‏‏‏‏ "إِذَا أَحْسَنَ أَحَدُكُمْ إِسْلَامَهُ، ‏‏‏‏‏‏فَكُلُّ حَسَنَةٍ يَعْمَلُهَا تُكْتَبُ لَهُ بِعَشْرِ أَمْثَالِهَا إِلَى سَبْعِ مِائَةِ ضِعْفٍ، ‏‏‏‏‏‏وَكُلُّ سَيِّئَةٍ يَعْمَلُهَا تُكْتَبُ لَهُ بِمِثْلِهَا".

SAHIH HADITH:

Narrated Abu Huraira: Allah's Apostle 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.

REFERENCE:

Sahih Al Bukhari 1: Chapter 2, Hadith 42