كتاب الطلاق
18  
The Book of Divorce
(1)
Chapter: 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
(1)
باب تَحْرِيمِ طَلاَقِ الْحَائِضِ بِغَيْرِ رِضَاهَا وَأَنَّهُ لَوْ خَالَفَ وَقَعَ الطَّلاَقُ وَيُؤْمَرُ بِجْعَتِهَا
Sahih Muslim 1471 o

Anas b. Sirin reported:

I asked Ibn 'Umar (Allah be pleased with them) about the woman whom he had divorced. He said: I divorced her while she was in the state of menses. It was mentioned to 'Umar (Allah be pleased with him) and he then made a mention of that to Allah's Apostle (ﷺ), whereupon he said: Command him to take her back and when the period of menses is over, then (he may divorce her in the state of her purity. He (Ibn Umar) said: So I took her back, then divorced her in her purity. I (the narrator) said: Did you count that divorce which you pronounced in the state of menses? He said: Why should I not have counted that? Was I helpless or foolish?
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا خَالِدُ بْنُ عَبْدِ اللَّهِ، عَنْ عَبْدِ الْمَلِكِ، عَنْ أَنَسِ بْنِ، سِيرِينَ قَالَ سَأَلْتُ ابْنَ عُمَرَ عَنِ امْرَأَتِهِ الَّتِي، طَلَّقَ فَقَالَ طَلَّقْتُهَا وَهْىَ حَائِضٌ فَذُكِرَ ذَلِكَ لِعُمَرَ فَذَكَرَهُ لِلنَّبِيِّ صلى الله عليه وسلم فَقَالَ ‏ "‏ مُرْهُ فَلْيُرَاجِعْهَا فَإِذَا طَهَرَتْ فَلْيُطَلِّقْهَا لِطُهْرِهَا ‏"‏ ‏.‏ قَالَ فَرَاجَعْتُهَا ثُمَّ طَلَّقْتُهَا لِطُهْرِهَا ‏.‏ قُلْتُ فَاعْتَدَدْتَ بِتِلْكَ التَّطْلِيقَةِ الَّتِي طَلَّقْتَ وَهْىَ حَائِضٌ قَالَ مَا لِيَ لاَ أَعْتَدُّ بِهَا وَإِنْ كُنْتُ عَجَزْتُ وَاسْتَحْمَقْتُ ‏.‏
Reference : Sahih Muslim 1471o
In-book reference : Book 18, Hadith 15
USC-MSA web (English) reference : Book 9, Hadith 3486
  (deprecated numbering scheme)