Hadith
حَدَّثَنَا يَزِيدُ، أَخْبَرَنَا عَبْدُ الْمَلِكِ، عَنْ أَنَسِ بْنِ سِيرِينَ، قَالَ قُلْتُ لِابْنِ عُمَرَ حَدِّثْنِي عَنْ طَلَاقِكَ، امْرَأَتَكَ قَالَ طَلَّقْتُهَا وَهِيَ حَائِضٌ قَالَ فَذَكَرْتُ ذَلِكَ لِعُمَرَ بْنِ الْخَطَّابِ رَضِيَ اللَّهُ عَنْهُ فَذَكَرَهُ لِلنَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مُرْهُ فَلْيُرَاجِعْهَا فَإِذَا طَهُرَتْ فَلْيُطَلِّقْهَا فِي طُهْرِهَا قَالَ قُلْتُ لَهُ هَلْ اعْتَدَدْتَ بِالَّتِي طَلَّقْتَهَا وَهِيَ حَائِضٌ قَالَ فَمَا لِي لَا أَعْتَدُّ بِهَا وَإِنْ كُنْتُ قَدْ عَجَزْتُ وَاسْتَحْمَقْتُ.
I asked Ibn `Umar about his wife whom he divorced. He said: I divorced her when she was menstruating, and I told ‘Umar about that, and he told the Prophet (ﷺ) , who said: `Tell him to take her back, then when she becomes pure, he may divorce her when she is pure.” He said: So I took her back, then I divorced her when she was pure. I said: Was that divorce that you gave her when she was menstruating counted as such?` He said: Why wouldn`t I count it? It must be counted even if I failed and acted foolishly.
Musnad Ahmad 36451·Also available on sunnah.com·