The prohibition of divorcing a menstruating woman without her consent; If a man breaks this rule, it still counts as a divorce, and he should be ordered to take her back
وَحَدَّثَنَاهُ أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَابْنُ الْمُثَنَّى، قَالاَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ إِدْرِيسَ، عَنْ عُبَيْدِ اللَّهِ، بِهَذَا الإِسْنَادِ . نَحْوَهُ وَلَمْ يَذْكُرْ قَوْلَ عُبَيْدِ اللَّهِ لِنَافِعٍ . قَالَ ابْنُ الْمُثَنَّى فِي رِوَايَتِهِ فَلْيَرْجِعْهَا . وَقَالَ أَبُو بَكْرٍ فَلْيُرَاجِعْهَا .
A hadith like this has been narrated on the authority of 'Ubaidullah, but he made no mention of the words of Ubaidullah that he said to Nafi'.