Nikah halala is one of the most bizarre aspects of Islamic law. It is a temporary marriage that allows a woman to return to her previous husband after a divorce. If her husband says “I divorce you” to her three times, she can’t return to him unless and until she marries another man, consummates the marriage, and is in turn divorced by the new husband. This is based on the Qur’an. Allah’s regulations for divorce emphasize regarding women that “men have a degree over them” (Qur’an 2:228). This may be why men can divorce their wives simply by saying, “Talaq” — You are divorced, or I divorce you. Such an easy procedure leads to divorces in a fit of pique, followed by reconciliation — and the Qur’an anticipates this and attempts to head it off by stipulating that a husband who divorces his wife three times cannot reconcile with her until she marries another man and is in turn divorced by him: “And if he has divorced her [for the third time], then she is not lawful to him afterward until she marries a husband other than him” (Qur’an 2:230).
“Muslim Woman Marries 65-Year-Old For Nikah Halala, But He Now Refuses To ‘Release’ Her For Remarriage,” Swarajya, October 24, 2018 (thanks to The Religion of Peace):