Sahih Muslim 1471mBook 18, Hadith 13
وَحَدَّثَنِي يَعْقُوبُ بْنُ إِبْرَاهِيمَ الدَّوْرَقِيُّ، عَنِ ابْنِ عُلَيَّةَ، عَنْ يُونُسَ، عَنْ مُحَمَّدِ بْنِ، سِيرِينَ عَنْ يُونُسَ بْنِ جُبَيْرٍ، قَالَ قُلْتُ لاِبْنِ عُمَرَ رَجُلٌ طَلَّقَ امْرَأَتَهُ وَهْىَ حَائِضٌ فَقَالَ أَتَعْرِفُ عَبْدَ اللَّهِ بْنَ عُمَرَ فَإِنَّهُ طَلَّقَ امْرَأَتَهُ وَهْىَ حَائِضٌ فَأَتَى عُمَرُ النَّبِيَّ صلى الله عليه وسلم فَسَأَلَهُ فَأَمَرَهُ أَنْ يَرْجِعَهَا ثُمَّ تَسْتَقْبِلَ عِدَّتَهَا . قَالَ فَقُلْتُ لَهُ إِذَا طَلَّقَ الرَّجُلُ امْرَأَتَهُ وَهْىَ حَائِضٌ أَتَعْتَدُّ بِتِلْكَ التَّطْلِيقَةِ فَقَالَ فَمَهْ أَوَإِنْ عَجَزَ وَاسْتَحْمَقَ.
I said to Ibn'Umar (Allah be pleased with them): A person divorcedhis wife while she was in the state of menses, whereupon he said: Do you know 'Abdullah b. Umar (Allah be pleased with them), for he divorced his wife in the state of menses. 'Umar (Allah be pleased with him) came to Allah's Apostle (ﷺ) and asked him, and he (the Holy Prophet) commanded him that he should take her back, and she started her 'Idda. I said to him: When a person divorces his wife, and she is in the state of menses, should that pronouncement of divorce be counted? He said: Why not, was he hopless or foolish?