Sahih Muslim Book - 1, Hadith - 334

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ وَزُهَيْرُ بْنُ حَرْبٍ وَإِسْحَاقُ بْنُ إِبْرَاهِيمَ وَاللَّفْظُ لِأَبِي بَكْرٍ قَالَ إِسْحَاقُ أَخْبَرَنَا سُفْيَانُ وَقَالَ الْآخَرَانِ حَدَّثَنَا ابْنُ عُيَيْنَةَ عَنْ أَبِي الزِّنَادِ عَنْ الْأَعْرَجِ عَنْ أَبِي هُرَيْرَةَ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ اللَّهُ عَزَّ وَجَلَّ إِذَا هَمَّ عَبْدِي بِسَيِّئَةٍ فَلَا تَكْتُبُوهَا عَلَيْهِ فَإِنْ عَمِلَهَا فَاكْتُبُوهَا سَيِّئَةً وَإِذَا هَمَّ بِحَسَنَةٍ فَلَمْ يَعْمَلْهَا فَاكْتُبُوهَا حَسَنَةً فَإِنْ عَمِلَهَا فَاكْتُبُوهَا عَشْرًا.

It was narrated that Abu Hurairah said: "The Messenger of Allah (s.a.w) said: 'Allah, the Mighty and Sublime, said: If My slave thinks of doing a bad deed, then do not write it down for him. Then if he does it, write it down as one bad deed. If he thinks of doing a good deed then he does not do it, write it down as one good deed, and if he does it, write it down tenfold.'"