What is the ruling regarding a fifth marriage that took place without the wife's knowledge of the existence of four other wives? Does it entail expiation, or does it affect the legitimacy of the children and the inheritance?

The scholars are unanimous on the impermissibility of combining more than four wives at one time, based on the Almighty's saying: "Then marry such women as seem good to you, two, three, or four," and on the saying of the Prophet, peace and blessings be upon him, to Ghaylan ibn Salamah when he embraced Islam and had ten wives: "Keep four and divorce the rest."

If a man marries a fifth wife, her marriage is annulled by scholarly consensus. If the wife does not know that she is the fifth, there is no blame on her and no expiation.

The lineage of the children of the woman whom the man married as a fifth wife is attributed to him, and they are entitled to inherit from him. As for her, she does not inherit from him because she is not a lawful wife. She is entitled to the dower she received in exchange for her enjoyment.