Does a major, irrevocable divorce (baynunah kubra) occur if a man divorces his wife three times in a short period, then takes her back eighteen years later, given that he does not recall the second divorce that the wife claims?

A man's forgetfulness of a divorce does not nullify it. If the wife is certain that three divorces have been pronounced, then she becomes unlawful to him with a major irrevocable divorce (baynunah kubra), and it is not permissible for him to return to her until she marries another husband. The husband's intention not to irrevocably separate from her is of no consequence.

If the husband does not admit to three divorces, and the wife has no proof for the third divorce, then his word is to be accepted, and he is to be believed. It has been said that he should be made to swear an oath, and then he and his wife should be left alone. However, it is not permissible for her to allow him to have conjugal relations with her as long as she is certain that three divorces have occurred, based on the statement of Ibn Qudamah: "If a woman claims that her husband divorced her, and he denies it, then his word is to be accepted, because the original state is the continuation of the marriage and the absence of divorce, unless she has proof for what she claims." And the statement of Ibn Al-Hammam: "The wife is like a judge; it is not permissible for her to allow him to have conjugal relations with her if she knows from him that which outwardly contradicts his claim."

Some scholars have obliged the wife to ransom herself from him with whatever she can, to free herself from falling into the unlawful with him, and this is a sound opinion.

Accordingly, this is a complex issue and must be referred to a court of law.