“Forbidden to you in marriage are your mothers and your daughters” (and the rest of the verse), encompass anyone designated a daughter, so that both his daughter’s daughter and his son’s daughter are forbidden to him in marriage. This differs from His words concerning inheritance:

“Allah instructs you concerning your children.”

This encompasses only his own children and his son’s children, not his daughter’s children. Since the terms “son” and “daughter,” when unqualified, encompass anyone so designated, Allah Most High said:

“And the wives of your sons who are from your own loins.”

This excludes an adopted son, such as Zayd, who used to be called Zayd ibn Muhammad. They called him a “son,” so had the wording been left unqualified, he might have been thought to fall within its scope. Thus, Allah Most High said, “who are from your own loins,” to exclude that case.

He permitted Muslim men to marry the former wives of their adopted sons, saying:

“So when Zayd had no further need of her, We gave her to you in marriage, so that there would be no restriction upon the believers concerning the wives of their adopted sons when they have no further need of them.”

Thus, if the terms “son” and “daughter” encompass everyone affiliated to a person—to the extent that Allah has forbidden him to marry his daughter through breastfeeding—then his daughter born of illicit intercourse is also called his “daughter.” She therefore has an even stronger claim to be forbidden to him in marriage under Islamic law and to be included within the verse establishing that prohibition. This is the position of Abū Hanīfah and his followers, Mālik and his followers, Ahmad ibn Hanbal and his followers, and the overwhelming majority of the imams of the Muslims.

The well-known disagreement among the Companions, the Successors, and those after them concerns whether illicit intercourse establishes marriage prohibitions through affinity. Thus, if a man wishes to marry the woman’s mother or her daughter by another man, this is a matter of longstanding disagreement among the early generations. Many scholars have upheld each position. Al-Shāfiʿī and Mālik, according to one of the two reports from him, permit it; Abū Hanīfah, Ahmad, and Mālik, according to the other report, prohibit it. In this matter, it is permissible for a person to follow either of the two scholarly positions. And Allah knows best.