He divorced his wife while she was menstruating, and Umar mentioned this to the Prophet ﷺ. The Messenger of Allah ﷺ said, "Tell him to take her back, then let him divorce her when she becomes pure or while she is pregnant."
حدثنا عثمان بن أبي شيبة حدثنا وكيع عن سفيان عن محمد بن عبد الرحمن مولى آل طلحة عن سالم
أنه طلق امرأته وهي حائض فذكر ذلك عمر للنبي ﷺ فقال رسول الله ﷺ مره فليراجعها ثم ليطلقها إذا طهرت أو وهي حامل
Sahih Muslim narrated it in the Book of Divorce, chapter on the prohibition of divorcing a menstruating woman without her consent, etc, hadith 5/1471, from the hadith of Waki, through him.