صحيح البخاري Sahih Bukhari كتاب الطلاق The Book of Divorce
بَابُ إِذَا طُلِّقَتِ الْحَائِضُ يُعْتَدُّ بِذَلِكَ الطَّلاَقِ:

(2) Chapter. If a woman is divorced during her menses, then that divorce is counted as one legal divorce.

2 hadith
Hadith 5252
حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ ، حَدَّثَنَا شُعْبَةُ ، عَنْ أَنَسِ بْنِ سِيرِينَ ، قَالَ : سَمِعْتُ ابْنَ عُمَرَ ، قَالَ : " طَلَّقَ ابْنُ عُمَرَ امْرَأَتَهُ وَهِيَ حَائِضٌ ، فَذَكَرَ عُمَرُ لِلنَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ، فَقَالَ : لِيُرَاجِعْهَا ، قُلْتُ : تُحْتَسَبُ ، قَالَ : فَمَهْ " . وَعَنْ قَتَادَةَ ، عَنْ يُونُسَ بْنِ جُبَيْرٍ ، عَنْ ابْنِ عُمَرَ ، قَالَ : مُرْهُ فَلْيُرَاجِعْهَا ، قُلْتُ : تُحْتَسَبُ ، قَالَ : أَرَأَيْتَ إِنْ عَجَزَ وَاسْتَحْمَقَ .
Narrated Anas bin Seereen: Ibn `Umar said: "I divorced my wife while she was menstruating. `Umar mentioned that to the Prophet . The Prophet said, (to my father), "Let your son take her back." I asked (Ibn `Umar), "Is such a divorce counted (i.e. as one legal divorce)?" Ibn `Umar said, "Of course." Narrated Yunus bin Jubair: Ibn `Umar said, "The Prophet said to `Umar, 'Order him (Ibn `Umar) to take her back.' " I asked, "Is such a divorce counted (as one legal divorce)?" Ibn `Umar said, "What do you think if someone becomes helpless and foolish?"
Hadith Reference Sahih Bukhari / The Book of Divorce / Hadith: 5252
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة
Hadith 5253
حَدَّثَنَا أَبُو مَعْمَرٍ ، حَدَّثَنَا عَبْدُ الْوَارِثِ ، حَدَّثَنَا أَيُّوبُ ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ ، عَنْ ابْنِ عُمَرَ ، قَالَ : حُسِبَتْ عَلَيَّ بِتَطْلِيقَةٍ .
Narrated Ibn `Umar: (Divorcing my wife during her menses) was counted as one legal divorce.
Hadith Reference Sahih Bukhari / The Book of Divorce / Hadith: 5253
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة