The ruling on one who contracted marriage with a woman but her twin sister was brought to him

Question:
We present to his Eminence the first letter, which came from the listener: Fadel Muhammad Ahmad from Sudan. His question says: A man proposed to one of the girls, and she has a twin sister. After the marriage contract was completed for the girl he chose, in the presence of witnesses, he was surprised on the wedding night to find that her sister had been brought to him. However, he had intercourse with her, and we do not know whether it was with his knowledge or without it. What is the ruling in both cases, and on whom does the sin fall? And what must he do?

Answer:
In the name of Allah, the Most Gracious, the Most Merciful.
Praise be to Allah, and may Allah send blessings and peace upon the Messenger of Allah, and upon his family and his Companions, and upon those who follow his guidance. As for what follows:
This is a matter that requires detailed explanation:
If he had intercourse with her while believing she was his wife, the one he had contracted with, then he owes nothing, and there is no sin on him. If she becomes pregnant, the child is attributed to him, because it is intercourse under doubt, and he is excused.
As for those who brought her to him, there is also a detailed explanation regarding them:
If they made a mistake, they owe nothing.
If they did it intentionally, then the sin is on them, and they deserve punishment for this bad, reprehensible act.
Then, after that, he has the choice:
If he wishes, he can divorce her sister and contract with her, because her sister has no waiting period; she is divorced and not entered upon. So he can divorce her and marry the sister who was brought to him immediately.
If he wishes, he can leave the one who was brought to him, because she is not his wife, if he is informed and made aware. His wife remains the one he contracted with.
There is no harm in his having intercourse with her, because this is intercourse under doubt, and she is not his wife, and he does not combine them in one contract.
It may be said that he must refrain from intercourse with the second one because of the intercourse with her sister, but this is not apparent, because this intercourse is intercourse under doubt, not intentional intercourse, and not marital intercourse, so he is excused in this. Yes.

The presenter: May Allah bless you.

The Shaykh: We previously discussed the case of the one to whom his wife's sister was brought. We said that he may enjoy his wife, the one he contracted with, if he does not desire the one who was brought to him and does not desire to marry her, even if he had intercourse with her.
But it occurred to me that there is a doubt in this: if he had intercourse with her, may he enjoy her sister, the one he contracted with, or not? This is a matter for consideration. Perhaps this will come up in the next session, if Allah wills, so that we can point this out after reviewing the words of the scholars on this, reflecting on this topic, and being cautious in this matter: is it permissible for him to have intercourse with his wife, the one he contracted with, while he had intercourse with her sister who was brought to him by mistake, or not? This is the point of difficulty.
We said that there is no harm, previously, in his having intercourse with his wife, the one he contracted with, even if he had intercourse with her sister by mistake. This is what is currently apparent and obvious. But it occurred to me that there is some doubt in the matter that requires re-examination. We may clarify this, if Allah wills, in the next session next week, if Allah wills.

The presenter: If Allah wills.

The Shaykh: May Allah guide them all.

The Shaykh: A question was raised in the previous session where we deferred the answer to part of it to this session. We would like to clarify it now. It is: a man contracted with one of two sisters, but the one not contracted with, her sister, was brought to him. What is the ruling?
It was previously stated that this must be examined. If he did not have intercourse with her and did not have contact with her, it does not harm him. He returns her to her family, and his wife remains in his possession, the one he contracted with, and he can ask for her whenever he wishes. If he desires the second one who was brought to him and wants her, there is no harm in marrying her from her family after he divorces her sister. She has no waiting period, because divorce without entry does not entail a waiting period. If he divorces her sister, whom he did not enter upon, and marries the second one who was brought to him, there is no harm.

The presenter: But with a contract?

The Shaykh: With a new contract.

The presenter: With a contract, yes.

The Shaykh: As for if he had intercourse with her while believing she was his wife, this is called intercourse under doubt. In this case, it does not invalidate the marriage of his wife, the one he contracted with, who is her sister. But as for this one he had intercourse with, is he required to refrain from his wife until she is purified, or not?
In the previous session, we paused on this. Is he required to pause until she is purified from this intercourse, because she may be pregnant, or she may not be pregnant? The obligatory thing is that she be purified by one menstruation or three menstruations, according to scholarly disagreement. A large number of scholars held that she is purified by three menstruations, like the waiting period of divorce. If it appears she is pregnant, her waiting period is the delivery of the child.
As for the second opinion that she is purified by one menstruation, one menstruation is sufficient to know the purity of the womb, like the fornicator, and like the one divorced by khul' on the correct opinion, and like the one being purified: the slave woman being purified after purchase or after sale. One menstruation is sufficient for her, according to some scholars, as purification for her, purification of her womb. And he may have intercourse with his wife who is with him after that.
This is the apparent statement of the scholars after we reviewed the words of the scholars. The apparent statement of the scholars is: he does not approach his wife with intercourse until he purifies her sister who was brought to him by mistake and he had intercourse with her. If she did not become pregnant, he purifies her by one menstruation, or three menstruations, according to disagreement. If she became pregnant, he refrains from his wife until she delivers the child. There is something in the soul about this, and we will follow up on the issue, if Allah wills. But what appears from the words of the scholars is: it is necessary to purify her by one menstruation on the most correct opinion, as chosen by Shaykh al-Islam Ibn Taymiyyah (may Allah have mercy on him), or by three menstruations, by analogy to the divorced woman. If she is pregnant, it is necessary for her to deliver the child. When she delivers or is purified, he may then have contact with his wife.
As for if we make intercourse under doubt like fornication, then fornication does not spread prohibition on the correct opinion, and it does not establish the ruling of affinity. If we analogize intercourse under doubt to that, then it is permissible for him to approach his wife, the one he contracted with, because this intercourse was followed by intercourse, because in meaning it resembles fornication, because it is not lawful. He was only permitted to attribute the child to him and that it is his, because he did not intend fornication. The matter was confused for him; he believed she was his wife, so he was excused and did not sin, because of his mistake. The child is attributed to him, because it is intercourse under doubt, so the child is attributed to him, as the scholars said.
But it resembles fornication in another aspect, which is that it is intercourse without a Shari'ah contract, and without Shari'ah ownership, so it resembles fornication. Therefore, it does not prevent the permissibility of the wife. This is the aspect of the opinion that it does not prevent. But if he is cautious and refrains from his wife until he purifies her sister by one menstruation, or three menstruations, or by delivery of the child, this is what should be done, as the scholars explicitly stated.
As for fornication: if he had fornicated with his wife's sister, or her aunt, or her maternal aunt, the correct opinion is that his wife does not become prohibited to him because of that. Rather, he may have contact with his wife. This intercourse is forbidden intercourse, so it does not entail prohibition, and it does not establish the prohibition of affinity if it was her mother or her daughter, on the correct opinion. And because it is a heinous act that should not be publicized, ruling that this intercourse has the ruling of lawful intercourse is what spreads the heinous act, publicizes the heinous act, and people ask: why? And it is said: because he had intercourse with so-and-so, he fornicated with so-and-so. This involves publicizing the heinous act.
Therefore, the correct opinion is that it does not spread prohibition, and it does not have the ruling of affinity intercourse. Rather, it is a void intercourse that does not spread prohibition and does not prevent approaching his wife. And on him is what is on the fornicator of the Shari'ah limit, if he was a fornicator.
And so, this one to whom his wife's sister was brought, and he knew she was his wife's sister, and he had no doubt, then he had intercourse with her, has the ruling of the fornicator. And on him is the limit of the fornicator: if he was a virgin, he is flogged one hundred times, and if he was a non-virgin, he is stoned, because he intentionally had fornication. And so, if she knew that he was not her husband, that the one contracted with was her sister, and she was brought to him by mistake, or they were confused about it.
The point is: if she knew that he was not her husband, and that he was mistaken about her, and that the marriage was for her sister, and she intentionally fornicated, then she has the ruling of the fornicator, because she intentionally allowed him to have access to herself, while she knew she was not his wife, but she preferred desire and Satan, we seek refuge in Allah. So she has the ruling of fornicators, and on her is the limit of the fornicator. As for him, he is excused if he did not know, and the matter was confused for him, believing she was his contracted wife. So he is excused, and the intercourse in his case is intercourse under doubt, which entails kinship. She is not excused if she knew that he was not her husband and that the ruling pertained to her sister, but she intentionally committed the heinous act. So she has the ruling of fornicators. As for him, he does not have the ruling of the fornicator, but he is excused, because the matter was confused for him and he did not know.
This is the detailed explanation we promised earlier. I hope the questioner is clear in this matter. And we ask Allah for guidance and success for everyone. Yes.

The presenter: May Allah reward you and grant you reward. If it becomes clear that this sister who was married to him is pregnant, is the child his son?

The Shaykh: It is attributed to him.

The presenter: Is it his son in the Shari'ah?

The Shaykh: Because it is a sexual intercourse based on a doubt. If he did not know that she was not his wife and he considered her to be his wife, then this child is attributed to him; because it falls under the category of intercourse based on doubt, and intercourse based on doubt results in the attribution of lineage. He has the right to contract marriage with her, as mentioned earlier, if he desires her. He can contract marriage with her through a new marriage contract after he divorces her sister whom he previously married; because there is no waiting period for her sister due to the fact that he married her but did not consummate the marriage, and a divorced woman with whom no consummation took place has no waiting period.

The presenter: He must refrain from her sister until she gives birth, if she is pregnant, or until she is purified by two or three menstrual cycles.

The Shaykh: This is the apparent statement of the scholars of knowledge; this is necessary. They argued with a hadith they narrated from the Prophet (peace and blessings be upon him), whose authenticity I do not know; it needs to be reviewed. It is that he (peace and blessings be upon him) said: And in another wording: They argued with this. If it is authentic, then it is an apparent proof, especially in the case of intentional action, for it is not permissible without any disagreement among all the scholars of knowledge. However, if it occurred by mistake, this is the matter under consideration. If it occurred by mistake, he is not held accountable for it; because he did not intend it. Rather, this is if it occurred intentionally, then he bears the responsibility for this matter which he intended. Yes.

The presenter: May Allah bless you.