that he had divorced his wife while she was menstruating during the lifetime of Messenger of Allah ﷺ . ʿUmar bin Al-Khattab asked Messenger of Allah ﷺ about that. Messenger of Allah ﷺ said, "Order him (your son) to take her back and keep her till she is clean and then to wait till she gets her next period and becomes clean again, whereupon, if he wishes to keep her, he can do so, and if he wishes to divorce her he can divorce her before having sexual intercourse with her; and that is the prescribed period which Allah has fixed for the women meant to be divorced."  

أَنَّهُ طَلَّقَ امْرَأَتَهُ وَهْىَ حَائِضٌ عَلَى عَهْدِ رَسُولِ اللَّهِ ﷺ فَسَأَلَ عُمَرُ بْنُ الْخَطَّابِ رَسُولَ اللَّهِ ﷺ عَنْ ذَلِكَ فَقَالَ رَسُولُ اللَّهِ ﷺ مُرْهُ فَلْيُرَاجِعْهَا ثُمَّ لِيُمْسِكْهَا حَتَّى تَطْهُرَ ثُمَّ تَحِيضَ ثُمَّ تَطْهُرَ ثُمَّ إِنْ شَاءَ أَمْسَكَ بَعْدُ وَإِنْ شَاءَ طَلَّقَ قَبْلَ أَنْ يَمَسَّ فَتِلْكَ الْعِدَّةُ الَّتِي أَمَرَ اللَّهُ أَنْ تُطَلَّقَ لَهَا النِّسَاءُ  

Ibn ʿUmar divorced his wife while she was having her menses. ʿUmar asked the Prophet ﷺ who said, "Order him (your son) to take her back, and then divorced her before her period of the 'Iddah has elapsed." I asked Ibn ʿUmar, "Will that divorce (during the menses) be counted?" He replied, "If somebody behaves foolishly (will his foolishness be an excuse for his misbehavior)?"  

طَلَّقَ ابْنُ عُمَرَ امْرَأَتَهُ وَهْىَ حَائِضٌ فَسَأَلَ عُمَرُ النَّبِيَّ ﷺ فَأَمَرَهُ أَنْ يُرَاجِعَهَا ثُمَّ يُطَلِّقَ مِنْ قُبُلِ عِدَّتِهَا قُلْتُ فَتَعْتَدُّ بِتِلْكَ التَّطْلِيقَةِ قَالَ أَرَأَيْتَ إِنْ عَجَزَ وَاسْتَحْمَقَ