"If it is the first or second divorce, the Messenger of Allah would tell him to take her back and keep her until she has menstruated again and purified herself, then divorce her before having intercourse with her. But if it was three simultaneous divorces, then you have disobeyed Allah with regard to the way in which divorce should be conducted and your wife has become irrevocably divorced." (Using translation from Nasāʾī 3557)
عَنِ رَجُلٍ طَلَّقَ امْرَأَتَهُ وَهِيَ حَائِضٌ فَيَقُولُ أَمَّا إِنْ يُطَلِّقَهَا وَاحِدَةً أَوِ اثْنَتَيْنِ فَإِنَّ رَسُولَ اللهِ ﷺ «أَمَرَهُ أَنْ يُرَاجِعَهَا ثُمَّ يُمْسِكَهَا حَتَّى تَحِيضَ حَيْضَةً أُخْرَى ثُمَّ تَطْهُرَ ثُمَّ يُطَلِّقَهَا قَبْلَ أَنْ يَمَسَّهَا وَأَمَّا أَنْ يُطَلِّقَهَا ثَلَاثًا فَقَدْ عَصَيْتَ اللهَ فِيمَا أَمَرَكَ بِهِ مِنْ طَلَاقِ امْرَأَتِكَ وَبَانَتْ مِنْكَ امْرَأَتُكَ»