Sahih Muslim Book - 1, Hadith - 337

و حَدَّثَنَا أَبُو كُرَيْبٍ حَدَّثَنَا أَبُو خَالِدٍ الْأَحْمَرُ عَنْ هِشَامٍ عَنْ ابْنِ سِيرِينَ عَنْ أَبِي هُرَيْرَةَ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مَنْ هَمَّ بِحَسَنَةٍ فَلَمْ يَعْمَلْهَا كُتِبَتْ لَهُ حَسَنَةً وَمَنْ هَمَّ بِحَسَنَةٍ فَعَمِلَهَا كُتِبَتْ لَهُ عَشْرًا إِلَى سَبْعِ مِائَةِ ضِعْفٍ وَمَنْ هَمَّ بِسَيِّئَةٍ فَلَمْ يَعْمَلْهَا لَمْ تُكْتَبْ وَإِنْ عَمِلَهَا كُتِبَتْ.

It was narrated that Abu Hurairah said: "The Messenger of Allah (s.a.w) said: 'Whoever thinks of doing a good deed and does not do it, one good deed will be written down for him. Whoever thinks of doing a good deed and does it, it will be written down between ten and seven-hundred fold. Whoever thinks of doing a bad deed and does not do it, it will not be written down, and if he does it, it will be written down."'