I asked him about the wife he had divorced during the time of the Messenger of Allah ﷺ. He said, "I divorced her while she was menstruating, so I mentioned that to Umar, and Umar mentioned it to the Prophet ﷺ. The Prophet ﷺ said, 'Order him to take her back. When she becomes pure, let him divorce her during her state of purity, in accordance with the Sunnah.'" He said, "So I did."Anas said, "I asked him, 'Did you count that divorce, the one you pronounced while she was menstruating?'"He replied, "Why would I not count it? Even if I had been incapable or acted foolishly?"
حدثنا محمد بن عبيد حدثنا عبد الملك يعني ابن أبي سليمان عن أنس بن سيرين
سألته عن امرأته التي طلق على عهد رسول الله ﷺ قال طلقتها وهي حائض فذكرت ذلك لعمر فذكره عمر للنبي ﷺ فقال النبي ﷺ مره فليراجعها إذا طهرت طلقها في طهرها للسنة قال ففعلت قال أنس فسألته هل اعتددت بالتي طلقتها وهي حائض قال وما لي لا أعتد بها إن كنت عجزت واستحمقت
Its isnad is sahih. Its meaning has already appeared repeatedly, both at length and in brief, the most recent being no. 6061. It has also appeared with similar wording through this same route, from Yazid bin Harun from Abdul-Malik, who is Ibn Abu Sulayman al-Arzami, within the musnad of Umar bin Khattab, under no. 304. Muslim likewise narrated it in his Sahih, 1:423, through the route of Khalid bin Abdullah al-Arzami.