“When one of you perfects.......

Abu Huraira reported: The Messenger of Allah, peace be upon him, said, “When one of you perfects his Islam, then every good deed he does is written as ten good deeds up to seven hundred times as much; and every bad deed he does is written as one bad deed.”
[Sahih al-Bukhari, Book 2, Number 41]

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

صحيح البخاري كِتَاب الْإِيمَانِ بَاب حُسْنُ إِسْلَامِ الْمَرْءِ