"Abdullah has divorced his wife while she was menstruating." He said: "Tell 'Abdullah to take her back, then leave her until she becomes pure from this menstrual period, then menstruates again, then when she becomes pure again, if he wishes he may separate from her before having intercourse with her, or if he wishes he may keep her. This is the time when Allah, the Mighty and Sublime, has stated that women may be divorced." (Using translation from Nasāʾī 3389)
أَنَّهُ طَلَّقَ امْرَأَتَهُ وَهِيَ حَائِضٌ فَأَتَى عُمَرُ النَّبِيَّ ﷺ فَاسْتَفْتَاهُ فَقَالَ مُرْ عَبْدَ اللهِ فَلْيُرَاجِعْهَا حَتَّى تَطْهُرَ مِنْحَيْضَتِهَا هَذِهِ ثُمَّ تَحِيضَ حَيْضَةً أُخْرَى فَإِذَا طَهُرَتْ فَلْيُفَارِقْهَا قَبْلَ أَنْ يُجَامِعَهَا أَوْ لِيُمْسِكْهَا فَإِنَّهَا الْعِدَّةُ الَّتِي أُمِرَ أَنْ تُطَلَّقَ لَهَا النِّسَاءُ