Sahih al-Bukhari 5269
Narrated Abu Huraira:
The Prophet (ﷺ) said, "Allah has forgiven my followers the evil thoughts that occur to their minds, as long 
as such thoughts are not put into action or uttered." And Qatada said, "If someone divorces his wife 
just in his mind, such an unuttered divorce has no effect.:
حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا هِشَامٌ، حَدَّثَنَا قَتَادَةُ، عَنْ زُرَارَةَ بْنِ أَوْفَى، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏
"‏ إِنَّ اللَّهَ تَجَاوَزَ عَنْ أُمَّتِي مَا حَدَّثَتْ بِهِ أَنْفُسَهَا، مَا لَمْ تَعْمَلْ أَوْ تَتَكَلَّمْ ‏"‏‏.‏ قَالَ قَتَادَةُ إِذَا طَلَّقَ فِي نَفْسِهِ فَلَيْسَ بِشَىْءٍ‏.‏