A man and woman who have committed fornication with one another may not marry one another unless they both repent. Then, if they repent, the question remains as to whether it would be lawful for them to marry while the woman is pregnant (i.e. still in her `iddah).
The answer to this question depends on whether or not the adulterer has the right to claim paternity for his child born of adultery.
The majority of the scholars are of the opinion that he may not claim paternity for the child. They say this on the basis of the hadîth where a dispute regarding the paternity of a child took place and the Prophet (peace be upon him) said: “The child is to be attributed to the one upon whose bed it is born, and for the adulterer there is stoning.” [Sahîh al-Bukhârî (2053) and Sahîh Muslim (1457)]
However, some of the Pious Predecessors, such as al-Hasan, Ibn Sîrîn, Ibrâhîm al-Nakha`î and Ishâq, held the opinion that it is permissible to attribute the child to the fornicator in cases where “the one upon whose bed it is born” – the woman’s husband, that is – does not claim paternity for the child. This is because the previous hadîth does not address such a case. It also does not address the case of an unmarried woman.
Moreover, `Umar attributed many children who were born before Islam to their biological fathers. [al-Muwatta’ (2/740), Musannaf `Abd al-Razzâq (7/303), and Sunan al-Bayhaqî (10/263)]
This is the correct opinion that is in conformity with reason and with the broad dictates of Islamic Law. It it the view that has been adopted by Ibn Taymiyah as well as by his student Ibn al-Qayyim. It is also the view that has been adopted by Sheikh Muhammad b. Sâlih al-`Uthaymîn.
Following this more correct opinion that the fornicator may claim paternity of his child as long as the woman’s husband does not do so, we say that this man can marry this woman who is pregnant from him as a result of their previous sexual intercourse.
This opinion is, moreover, one that has been adopted by some scholars. They permitted the fornicator to marry the woman with whom he had fornicated upon their repentance and during her waiting period (`iddah). However, no other man besides that fornicator may marry this woman while she is still in her `iddah to clear womb from that sexual intercourse.
The majority of the scholars are of the view that is impermissible for anyone – neither the fornicator nor any other man – to marry the woman who committed fornication, until except after their repentance and after the completion of her `iddah. This is because they hold the view that the child born of an illicit relationship cannot be attributed to the man with whom she conceived it. Therefore, she must establish that her womb is clear before she can marry him.
However, the correct view, as we have already discussed, is that the fornicator may marry the woman with whom he has committed fornication while she is still in her `iddah, as long as both of them have repented. This is because we uphold the view that he can claim paternity for any child that may have resulted from their illicit relationship.
Therefore, this man may marry this woman while she is still pregnant and the child resulting from their illicit relationship will be attributed to him, provided they have first repented from their sin.
As for the duration of the waiting period (`iddah) for a woman who has fornicated, it is the duration of one menstrual cycle unless she is pregnant. In the case of pregnancy, the woman’s waiting period comes to an end only upon delivery. This is according to the strongest saying of the people of knowledge. This is the view that has been adopted by Ibn Taymiyah and his student Ibn al-Qayyim, as well as by `Abd al-Rahmân al-Sa`dî and his student Muhammad b. Sâlih al- `Uthaymîn.
And Allah knows best.