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 Book 18, Hadith 16
← Previous Hadith I asked Ibn 'Umar (Allah be pleased with them) about the woman whom he had divorced. He said: I divorced her while she was in the state of menses. It was mentioned to 'Umar (Allah be pleased with him) and he then made a mention of that to Allah's Apostle (ﷺ), whereupon he said: Command him to take her back and when the period of menses is over, then (he may divorce her in the state of her purity. He (Ibn Umar) said: So I took her back, then divorced her in her purity. I (the narrator) said: Did you count that divorce which you pronounced in the state of menses? He said: Why should I not have counted that? Was I helpless or foolish?

Sahih Muslim Book 18, Hadith 15 Next Hadith → This hadith has been narrated on the authority of Shu'ba with the same chain of transmitters but with a slight variation in wording.

Sahih Muslim Book 18, Hadith 17