I asked Ibn Umar about a man who divorces his wife while she is menstruating.He replied, "Do you know Abdullah bin Umar?"I said, "Yes."He said, "He divorced his wife while she was menstruating, so Umar went to the Prophet ﷺ and asked him about it. The Prophet ﷺ instructed him to take her back, then divorce her later so that she could begin her waiting period properly."
حدثنا إسماعيل عن يونس عن محمد بن سيرين
سألت ابن عمر عن الرجل يطلق امرأته وهي حائض فقال أتعرف عبد الله بن عمر قلت نعم قال فإنه طلق امرأته وهي حائض فأتى عمر النبي ﷺ فسأله فأمره النبي ﷺ أن يراجعها ثم يطلقها فتستقبل عدتها