Verily Allah has fixed the very portion of adultery which a man will indulge in, and which he of necessity must commit. The adultery of the eye is the lustful look, and the adultery of the tongue is the licentious speech, the heart desires and yearns, which the parts may or may not put into effect.  

مَا رَأَيْتُ شَيْئًا أَشْبَهَ بِاللَّمَمِ مِمَّا قَالَ أَبُو هُرَيْرَةَ أَنَّ النَّبِيَّ ﷺ قَالَ إِنَّ اللَّهَ كَتَبَ عَلَى ابْنِ آدَمَ حَظَّهُ مِنَ الزِّنَى أَدْرَكَ ذَلِكَ لاَ مَحَالَةَ فَزِنَى الْعَيْنَيْنِ النَّظَرُ وَزِنَى اللِّسَانِ النُّطْقُ وَالنَّفْسُ تَمَنَّى وَتَشْتَهِي وَالْفَرْجُ يُصَدِّقُ ذَلِكَ أَوْ يُكَذِّبُهُ قَالَ عَبْدٌ فِي رِوَايَتِهِ ابْنِ طَاوُسٍ عَنْ أَبِيهِ سَمِعْتُ ابْنَ عَبَّاسٍ  

Abu Huraira reported Messenger of Allah ﷺ as saying. Allah fixed the very portion of adultery which a man will indulge in. There would be no escape from it. The adultery of the eye is the lustful look and the adultery of the ears is listening to voluptuous (song or talk) and the adultery of the tongue is licentious speech and the adultery of the hand is the lustful grip (embrace) and the adultery of the feet is to walk (to the place) where he intends to commit adultery and the heart yearns and desires which he may or may not put into effect.  

عَنِ النَّبِيِّ ﷺ قَالَ كُتِبَ عَلَى ابْنِ آدَمَ نَصِيبُهُ مِنَ الزِّنَى مُدْرِكٌ ذَلِكَ لاَ مَحَالَةَ فَالْعَيْنَانِ زِنَاهُمَا النَّظَرُ وَالأُذُنَانِ زِنَاهُمَا الاِسْتِمَاعُ وَاللِّسَانُ زِنَاهُ الْكَلاَمُ وَالْيَدُ زِنَاهَا الْبَطْشُ وَالرِّجْلُ زِنَاهَا الْخُطَا وَالْقَلْبُ يَهْوَى وَيَتَمَنَّى وَيُصَدِّقُ ذَلِكَ الْفَرْجُ وَيُكَذِّبُهُ