Urwa ibn al-Zubayr عروة بن الزبير · The Book on Divorce and Li'an

His father divorced his wife during her menses, so Umar asked the Prophet about that and he said: "Tell him to take her back, then let him divorce her while she is pure or pregnant."

'O Messenger of Allah! I irrevocably divorced my wife.' So he said: 'What did you intend by that?' I said: 'One (divorce).' He said: '(Do you swear) By Allah?' I said: 'By Allah.' He said: 'Then it is as you intended.'"

The Messenger of Allah said: "Allah has permitted my Ummah what occurs in their mines, as long as it is not spoken or acted upon."

The Messenger of Allah said: "Three are serious when they are serious, and serious when they are in jest: Marriage, divorce, and return."