the Prophet ﷺ said concerning a man who declared Zihar upon his wife having intercourse with her before compensation: "Let him offer one expiation."  

عَنِ النَّبِيِّ ﷺ فِي الْمُظَاهِرِ يُوَاقِعُ قَبْلَ أَنْ يُكَفِّرَ قَالَ كَفَّارَةٌ وَاحِدَةٌ  

a man declared Zihar upon his wife, then he had intercourse with her before offering expiation. He came to the Prophet ﷺ and told him about that. He said: "What made you do that?" He said: "I saw her ankles in the moonlight, and I could not control myself, and I had intercourse with her." The Messenger of Allah ﷺ smiled and told him not to go near her until he had offered expiation.  

أَنَّ رَجُلاً ظَاهَرَ مِنِ امْرَأَتِهِ فَغَشِيَهَا قَبْلَ أَنْ يُكَفِّرَ فَأَتَى النَّبِيَّ ﷺ فَذَكَرَ ذَلِكَ لَهُ فَقَالَ مَا حَمَلَكَ عَلَى ذَلِكَ فَقَالَ يَا رَسُولَ اللَّهِ رَأَيْتُ بَيَاضَ حِجْلَيْهَا فِي الْقَمَرِ فَلَمْ أَمْلِكْ نَفْسِي أَنْ وَقَعْتُ عَلَيْهَا فَضَحِكَ رَسُولُ اللَّهِ ﷺ وَأَمَرَهُ أَلاَّ يَقْرَبَهَا حَتَّى يُكَفِّرَ