Chapter 19: The Book of Divorce
Anas b. Sirin reported that he had heard Ibn 'Umar (Allah be pleased with them) as saying. I divorced my wife while she was in the state of menses. 'Umar (Allah be pleased with him) came to Allah' s Apostle (ﷺ) and informed him about it, whereupon he (Allah' s Apostle) said: Command him to take her back and when she is pure, then divorce her. I said to Ibn 'Umar Allah be pleased with them): Did you count that pronouncement of divorce? He said: Why not?
Sahih Muslim 1471p