What is the ruling on a woman irrevocably divorced with a major, final divorce (talaq bain baynunah kubra) marrying her divorcer after they committed adultery before the marriage, and she became pregnant from adultery, knowing that the irrevocable divorce was after two previous divorces, and then he divorced her a third time after discovering her pregnancy from adultery? And what are the conditions for marriage in the four schools of thought?

"Khul‘" (divorce at the wife's instance) is an annulment, not counted as a divorce, even if it occurs with the utterance of a divorce pronouncement. Therefore, it is permissible for the husband to marry his former wife (the one who sought khul‘) with a new contract after she has been divorced by him twice. The third divorce pronounced by the husband after the second marriage is valid, whether the marriage contract was sound or invalid. The marriage contract is considered sound if the pregnancy resulted from him and they repented from adultery. However, if the pregnancy was from someone else, or they did not repent, then the marriage contract is invalid. Nevertheless, a divorce pronounced within it is as valid as one pronounced in a sound marriage. If the husband divorces his wife for the third time, she is not permissible for him until she marries another man with the intention of a genuine marriage, not merely to become permissible for her first husband (tahleel), and then he divorces her or dies. Only then can she return to her first husband. A marriage contract is valid with the mutual consent of both parties, the woman's guardian (wali), and two Muslim witnesses.