Sahih Bukhari Volume 7, Book 68, Hadith 5260

حَدَّثَنَا حَجَّاجُ بْنُ مِنْهَالٍ، حَدَّثَنَا هَمَّامُ بْنُ يَحْيَى، عَنْ قَتَادَةَ، عَنْ أَبِي غَلاَّبٍ، يُونُسَ بْنِ جُبَيْرٍ قَالَ قُلْتُ لاِبْنِ عُمَرَ رَجُلٌ طَلَّقَ امْرَأَتَهُ وَهْىَ حَائِضٌ‏.‏ فَقَالَ تَعْرِفُ ابْنَ عُمَرَ إِنَّ ابْنَ عُمَرَ طَلَّقَ امْرَأَتَهُ وَهْىَ حَائِضٌ فَأَتَى عُمَرُ النَّبِيَّ صلى الله عليه وسلم فَذَكَرَ ذَلِكَ لَهُ فَأَمَرَهُ أَنْ يُرَاجِعَهَا فَإِذَا طَهُرَتْ فَأَرَادَ أَنْ يُطَلِّقَهَا فَلْيُطَلِّقْهَا، قُلْتُ فَهَلْ عَدَّ ذَلِكَ طَلاَقًا قَالَ أَرَأَيْتَ إِنْ عَجَزَ وَاسْتَحْمَقَ‏.

Narrated By Abi Ghallab Yunus bin Jubair : I asked Ibn 'Umar,"(What is said regarding) a man divorces his wife during her period?" He said, "Do you know Ibn 'Umar? Ibn 'Umar divorced his wife while she was menstruating. 'Umar then went to the Prophet and mentioned that to him. The Prophet ordered him to take her back and when she became clean, he could divorce her if he wanted." I asked (Ibn 'Umar), "Was that divorce counted as one legal divorce?" He said, "If one becomes helpless and foolish (will he be excused? Of course not)."