Abdullah bin Ayman asked Ibn 'Umar while Abu Az-Zubair was listening: "What did you think about a man who divorces his wife when she is menstruating?" He said to him: "Abdullah bin 'Umar divorced his wife when she was menstruating during the time of the Messenger of Allah. 'Umar asked the Messenger of Allah (about that) and said: “Abdullah bin 'Umar has divorced his wife while she was menstruating.' The Messenger of Allah said: “Let him take her back.' So he made me take her back. He said: “When she becomes pure, let him divorce her or keep her.' Ibn 'Umar said: “The Prophet said: “O Prophet! When you divorce women, divorce them before their 'Iddah (prescribed period) elapses”””””"
SahihSahihSahih MuslimBook 27 · Hadith 4