What happens to the legal status of a marriage if a man’s father commit’s adultery with that man’s wife, or if a woman’s mother commit’s adultery with her husband? Is the marriage immediately nullified on account of this, even if the husband and wife wish to stay together?
The preferred opinion is – as asserted by al-Shāfi`ī and by Mālik in one of the narrations from him – that this act does not result in the unlawfulness of marriage. Such a prohibition requires evidence, and there is no evidence from the Qur’ān, the Sunnah, nor is there consensus nor there any valid juristic analogy to support such an opinion.Ibn al-`Arabī writes: “In a case where no direct lineage can legally be established, it follows that no in-law relationship can be established. Therefore, fornication with a woman or her mother does not make marriage unlawful. What becomes unlawful by virtue of something lawful does not become unlawful on account of something unlawful.” [Tafsīr al-Qurtubī (13/59)]
It is incorrect to compare an unlawful sexual act to marriage in effecting a prohibition of marriage with near relatives. There are differences between the two. Allah has made the relationship by marriage (i.e. in-law relationships) the partner of biological lineage. It is a blessing which he has bestowed upon his servants. Both types of relationship are blessings and from His grace. The ties of kinship through marriage are not established by unlawful means any more than legitimate lineage is established by such means.
Indeed, if lineage – which is the most fundamental relationship – does not come about from unlawful sexual intercourse, then in-law relationships which are subsidiary and which resemble the blood relationships are even further from being established by way of unlawful sexual intercourse.
Moreover, had marriage been forbidden by an unlawful sexual relationship by virtue of it bringing about an in-law type of relationship, then it follows that a full mahram relationship would be established between the relevant parties as well. Since this is not the case, then the unlawfulness of marriage cannot be established either.
What is more, Allah says (in the verses enumerating prohibited degrees of marriage): “…and the wives (halā’il) of your sons” [Sūrah al-Nisā’: 23] Women whom a son had fornicated with are not called halā’il since the word literally means “those who are lawful to you”.
Allah says: “And marry not women whom your fathers married – except what is past.” [Sūrah al-Nisā’: 22]
What is meant here is marriage that is the very opposite of unlawful sexual relations. The word for marriage – nikāh – does not appear even once in the Qur’an with the meaning of fornication or referring to sex outside of the bonds of marriage.
This view is also supported by the fact that the rulings pertaining to marriage that Allah has set forth – the waiting period, mourning for widows, inheritance, lawful and prohibited degrees, attribution of lineage, the obligation of maintenance, that of dowry, the possibility of the khul` separation, of divorce, the oat of abstention, that of limiting a man to four women and that of justice between them, the ruling of revoking a divorce, that of consummated chastity, of restoring lawfulness to a former husband, and other such rulings – none of them apply to fornication and adultery, with the exception of some disagreement about the waiting period and dowry. However, the correct view is that there is no dowry for prostitution, as clearly stated in the Sunnah of Allah’s Messenger (peace be upon him). Also, the minds of people are naturally predisposed to having an aversion to it. Then, how can the prohibition of marriage on the basis of an in-law like relationship be established through fornication?
The Hanbalī position is that fornication and adultery are like marriage in that the mother and the daughters of a woman with whom a man has unlawful sexual relations with become permanently unlawful for that man to marry. This is one of the strange opinions in the body of knowledge in that it makes unlawful sex like marriage…Therefore, the opinion to be relied upon is that in the tragic event that someone’s parent commits adultery with that person’s spouse, the marriage is still intact and legally valid. It is not nullified.
The correct opinion is that nothing brings about prohibition of marriage through in-law relationships except a valid contract and that is because whenever Islamic Law mentions a contract in an unqualified statement, it refers to a valid contract. Therefore, the correct ruling on this matter is that what comes by way of an unlawful relationship does not bring about the prohibition of marriage similar to the prohibition of in-law relationships.