Sahih Muslim Book - 18, Hadith - 3664

وَحَدَّثَنِى يَعْقُوبُ بْنُ إِبْرَاهِيمَ الدَّوْرَقِىُّ 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 النَّبِىَّ -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

It was narrated that Yunus bin Jubair said: "I said to Ibn 'Umar: 'A man divorced his wife while she was menstruating.' He said: 'Do you know 'Abdullah bin 'Umar? He divorced his wife while she was menstruating, and 'Umar went to the Prophet (s.a.w) and asked him (about that), and he told him to take her back, so that she might start her 'Iddah."' He said: "I said to him: 'If a man divorces his wife while she is menstruating, does that count as a divorce?' He said: 'Of course; it must be counted even if he failed and acted foolishly."'