In Islam, fornication and adultery are grave sins and committing either bears serious consequences in this world and the hereafter. However, in a practical and matchless approach to prevent the crime of zina before its occurrence, Islam does not merely forbid the actual deeds, but Islam also declares each and every circumstance or avenue that may lead to fornication and adultery as forbidden. Allah Almighty says, “And come not near unto adultery. Lo! it is an abomination and an evil way.” (Al-Isra’: 32)
But those who commit this sin should not lose hope in Allah’s forgiveness as long as they repent and are determined to correct their lewd conduct. In fact, Islam encourages them to get united in marriage to have a lawful relationship particularly if their relationship results in pregnancy.
The eminent Muslim scholar, Sheikh Yusuf Al-Qaradawi, states: “When an adulterer and an adulteress repent to Allah (Exalted be He) in order to abandon the unlawful life and get into a lawful, pure one (as indicated from the question), then their marriage is legal and accepted by the consensus of Muslim scholars. The Islamic Center should welcome them, encourage them and do everything needed to complete the legal contract of marriage, and have this contract registered as an official document with the official circles, to protect the rights of both parties should a dispute arise or an allegation of denial be made.
The majority of jurists do not put repentance as a condition for validating marriage of an adulteress woman. It is reported that `Umar (may Allah be pleased with him) punished a man and a woman with lashing when they were found guilty of fornication, but he was keen after that on uniting them in marriage.
It is only the Hanbalites jurists who made the condition of repentance, acting on the Qur’anic verse: “The adulterer shall not marry save an adulteress or an idolatress, and the adulteress none shall marry save an adulterer or an idolater. All that is forbidden unto believers.” (An-Nur: 3)
However, the man and woman in our case are already repentant, as indicated from the information we have, and also by means of applying the rule of assuming the best in Muslims.
Concerning the `iddah and whether it behooves an adulteress to observe it or not, it is a bone of contention among Muslim jurists. What I pick out here is the opinion of the Hanafites, the Shafi`ites and al-Thawri: that an adulteress is not asked to observe `iddah, even if she is pregnant from zina (adultery or fornication). The same opinion is reported to have been adopted by three Companions/Caliphs: Abu-Bakr;
`Umar and `Ali (may Allah be pleased with them all). They based their judgment on the Hadith reported by both al-Bukhari and Muslim on the authority of `Aishah (may Allah be pleased with her): “Offspring are attributed to a legal wife, but a prostitute is entitled to nothing but the stones (stoning to death as a punishment).” The ‘iddah has basically been prescribed for making sure the woman has not an embryo in her womb, and for protecting men’s lineage and establishing paternity, and since this is not needed in cases of zina so there is no need for ‘iddah.
When a man gets married to a woman pregnant from zina with another man, his marriage is sound and valid in the opinion of Imam Abu-Hanifah and his disciple Imam Muhammad. Fatwas (religious opinions) are given to that effect under the Hanafi school of jurisprudence. Yet, such a man is not permitted to have a sexual intercourse with her until she delivers her baby, in accordance with the Prophetic hadith: “It is forbidden for a man who believes in Allah and the Hereafter to water the plant of another man (i.e. to marry and copulate with a woman who is pregnant from another man).” (Reported by Abu-Dawud, on the authority of Ruwayfi` ibn Thabit, and by At-Tirmidhi who held the Hadith as Hasan [of good chain of transmitters]).
This is different from the case when the woman’s pregnancy is from the adulterer himself, as in this case his getting married to her is permissible by agreement of both the Hanafites and some other scholars. In the opinion of all of them, it is lawful for this man to copulate with her upon marriage while she is pregnant, since the “plant” is his and he causes her gestation.”