Ibn ʿUmar bin Al-Khattab divorced his wife during her menses. Messenger of Allah ﷺ ordered him to take her back till she became clean, and when she got another period while she was with him, she should wait till she became clean again and only then, if he wanted to divorce her, he could do so before having sexual relations with her. And that is the period Allah has fixed for divorcing women. Whenever ʿAbdullah (bin ʿUmar) was asked about that, he would say to the questioner, "If you divorced her thrice, she is no longer lawful for you unless she marries another man (and the other man divorces her in his turn).' Ibn ʿUmar further said, 'Would that you (people) only give one or two divorces, because the Prophet ﷺ has ordered me so."
أَنَّ ابْنَ عُمَرَ بْنِ الْخَطَّابِ ؓ طَلَّقَ امْرَأَةً لَهُ وَهْىَ حَائِضٌ تَطْلِيقَةً وَاحِدَةً فَأَمَرَهُ رَسُولُ اللَّهِ ﷺ أَنْ يُرَاجِعَهَا ثُمَّ يُمْسِكَهَا حَتَّى تَطْهُرَ ثُمَّ تَحِيضَ عِنْدَهُ حَيْضَةً أُخْرَى ثُمَّ يُمْهِلَهَا حَتَّى تَطْهُرَ مِنْ حَيْضِهَا فَإِنْ أَرَادَ أَنْ يُطَلِّقَهَا فَلْيُطَلِّقْهَا حِينَ تَطْهُرُ مِنْ قَبْلِ أَنْ يُجَامِعَهَا فَتِلْكَ الْعِدَّةُ الَّتِي أَمَرَ اللَّهُ أَنْ تُطَلَّقَ لَهَا النِّسَاءُ وَكَانَ عَبْدُ اللَّهِ إِذَا سُئِلَ عَنْ ذَلِكَ قَالَ لأَحَدِهِمْ إِنْ كُنْتَ طَلَّقْتَهَا ثَلاَثًا فَقَدْ حَرُمَتْ عَلَيْكَ حَتَّى تَنْكِحَ زَوْجًا غَيْرَهُ وَزَادَ فِيهِ غَيْرُهُ عَنِ اللَّيْثِ حَدَّثَنِي نَافِعٌ قَالَ ابْنُ عُمَرَ لَوْ طَلَّقْتَ مَرَّةً أَوْ مَرَّتَيْنِ فَإِنَّ النَّبِيَّ ﷺ أَمَرَنِي بِهَذَا