and foster-daughter are likewise forbidden to him. They cite as evidence the general wording of Allah’s statement: “Your wives’ mothers” [al-Nisa 4:23]. A woman who breastfeeds is called a mother. They also cite: “Do not marry those women whom your fathers married” [al-Nisa 4:22]; and a foster-father is called a father; as well as His statement: “the wives of your sons,” and the Prophet’s saying: “Through breastfeeding, what is forbidden through lineage is also forbidden.” (1)

They say: Just as a husband’s biological father is forbidden to his wife, so too is his foster-father forbidden to her; and just as a wife’s biological mother is forbidden to her husband, so too is her foster-mother forbidden to him.

Shaykh al-Islam chose the view that breastfeeding does not render forbidden what is rendered forbidden through marital ties, based on the hadith: “Through breastfeeding, what is forbidden through lineage is also forbidden.” The explicit wording of the hadith indicates that breastfeeding renders forbidden whatever lineage renders forbidden, while its implied meaning indicates that breastfeeding does not render forbidden what is forbidden for a reason other than lineage.

As for Allah’s statement, “Your wives’ mothers,” citing it as evidence is invalid on the basis of the verse itself. If the unqualified term “mother” included both a foster-mother and a biological mother, then His statement, “your mothers who nursed you,” would serve no purpose, since “your mothers” had already occurred at the beginning of the verse. Moreover, a foster-mother cannot properly be called “mother” without qualification; the qualifier is indispensable. This is why she is not included in the term “mother” in Allah’s statement, “For his mother is one-sixth” [al-Nisa 4:11], by scholarly consensus. Likewise, when used without qualification, “sister” does not include a foster-sister; otherwise, He would not have said, “your foster-sisters.” Thus, there is no proof in the verse.