that the Prophet said, about the one who uttered Zihar and had intercourse before the atonement: "One atonement."  

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

A man came to the Prophet, and he had uttered Zihar upon his wife then he had intercourse with her. So he said: 'O Messenger of Allah! I uttered Zihar against my wife, then I had intercourse with her before atoning.' He (pbuh) said: "What caused you to do that, may Allah have mercy upon you?' He said: 'I saw her anklets in the moonlight.' He said: 'Then do not go near her until you have done what Allah ordered (for it).'"  

أَنَّ رَجُلاً أَتَى النَّبِيَّ ﷺ قَدْ ظَاهَرَ مِنِ امْرَأَتِهِ فَوَقَعَ عَلَيْهَا فَقَالَ يَا رَسُولَ اللَّهِ إِنِّي قَدْ ظَاهَرْتُ مِنْ زَوْجَتِي فَوَقَعْتُ عَلَيْهَا قَبْلَ أَنْ أُكَفِّرَ فَقَالَ وَمَا حَمَلَكَ عَلَى ذَلِكَ يَرْحَمُكَ اللَّهُ قَالَ رَأَيْتُ خُلْخَالَهَا فِي ضَوْءِ الْقَمَرِ قَالَ فَلاَ تَقْرَبْهَا حَتَّى تَفْعَلَ مَا أَمَرَكَ اللَّهُ بِهِ