It is mentioned on his authority regarding the one with whom adultery was committed that she is to undergo istibra' (17) by means of one menstrual cycle; this is because it is intercourse (18) outside of marriage, and its rulings are not the rulings of marriage. It is possible that her sister is not prohibited by that, nor are four others besides her, because she is not a wife (mankuhah), and mere intercourse does not prohibit, as evidenced by the fact that intercourse with a slave woman (milk al-yamin) does not prevent the marriage of four others besides her.

Section: If the husband claims that his wife informed him that her waiting period had ended within a period during which it is possible for it to have ended, and she denies it, it is permitted for him to marry her sister and four others besides her in the external (zahir) ruling. As for the inward (batin) ruling, it is based (19) on his truthfulness in that; for it is a right between him and Allah the Almighty, so his statement regarding it is accepted. However, he is not deemed truthful regarding the negation of her maintenance, her housing, and the negation of lineage, because these are rights for her and her child, so his statement is not accepted (20) regarding them. Al-Shafi'i and others held this view. Zufar said: He is not deemed truthful in any of it, because it is a single statement; if he is not deemed truthful in part of its ruling, he should not be deemed truthful in the other part, by drawing an analogy between the two. This is because it is not possible for a single statement to be both true and false. Our evidence is that it is a statement that entails the nullification of another's right and a right belonging to him which causes no harm to others, so it is necessary that he be deemed truthful in one of the two but not the other, just as if he purchased a slave and then confessed that the seller had emancipated him; he would be deemed truthful regarding his freedom, but not deemed truthful in reclaiming his price. Likewise (21), if he confessed that his wife was his sister through breastfeeding before consummation, he would be deemed truthful regarding her separation and the prohibition of her to him, but would not be deemed truthful regarding the cancellation of her dowry.

1140 - Issue; He said: (And whoever proposes to a woman, and [a contract] is performed on her behalf for someone else, the marriage is not concluded).

The meaning of this is that a man proposes to a specific woman and is answered with consent to that, but then the marriage is established for him with someone other than her, while he believes it is the one he proposed to, so he accepts. The marriage is not concluded because the acceptance was directed toward someone other than the one for whom the proposal was made, so it is invalid, just as if one bargained with him over a garment and established the contract on a different one without the buyer's knowledge. If he learned of the situation after that and consented, it would not be valid.