It was narrated from Ibn 'Umar that he divorced his wife when she was menstruating. 'Umar, may Allah be pleased with him, mentioned that to the Prophet (ﷺ) and he said:

"Tell him to take her back until she menstruates again, then when she becomes pure, if he wants he may divorce her and if he wants he may keep her. This is the divorce that Allah has enjoined. Allah, the Mighty and Sublime, says: 'The divorce is twice, after that, either you retain her on reasonable terms or release her with kindness.'"

حَدَّثَنَا بِشْرُ بْنُ خَالِدٍ، قَالَ حَدَّثَنَا يَحْيَى بْنُ آدَمَ، عَنِ ابْنِ إِدْرِيسَ، عَنْ مُحَمَّدِ بْنِ إِسْحَاقَ، وَيَحْيَى بْنِ سَعِيدٍ، وَعُبَيْدِ اللَّهِ بْنِ عُمَرَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، ح وَأَخْبَرَنَا زُهَيْرٌ، عَنْ مُوسَى بْنِ عُقْبَةَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالُوا إِنَّ ابْنَ عُمَرَ طَلَّقَ امْرَأَتَهُ وَهِيَ حَائِضٌ فَذَكَرَ عُمَرُ رضى الله عنه لِلنَّبِيِّ صلى الله عليه وسلم فَقَالَ ‏

‏ مُرْهُ فَلْيُرَاجِعْهَا حَتَّى تَحِيضَ حَيْضَةً أُخْرَى فَإِذَا طَهُرَتْ فَإِنْ شَاءَ طَلَّقَهَا وَإِنْ شَاءَ أَمْسَكَهَا فَإِنَّهُ الطَّلاَقُ الَّذِي أَمَرَ اللَّهُ عَزَّ وَجَلَّ بِهِ ‏

‏ ‏.‏ قَالَ تَعَالَى ‏{‏ فَطَلِّقُوهُنَّ لِعِدَّتِهِنَّ ‏}‏ ‏.‏