Yunus ibn Jabayr said that he asked Ibn Umar (RA)about a man who divorced this wife while she was menstruating. He asked him, “Do you know Abdullah ibn Umar? He had divorced his wife while she was menstruating. So Umar asked the Prophet (SAW) (about it) and he commanded him to (revoke and) take her back. Umar asked him if (the pronouncement of) the divorce would be counted and the Prophet said: Quiet! What, if he were helpless and mad (would that not have been reckoned)?’
[Bukhari 5252, Muslim 1741, Abu Dawud 2183, Nisai 3399, Ibn e Majah 2022]