only, not to his ascendants or collateral relatives. The author then derives a number of individual cases from this principle, saying:

“The nursing woman is lawful in marriage to the nursling’s father and his brother by blood.” Thus, the woman who nursed the child may be married by the child’s father. For example, if Fatimah nursed a child named Ali, it is permissible for Ali’s father to marry Fatimah, and it is likewise permissible for Ali’s brother to marry her, because neither of them is among the nursling’s descendants.

His statement, “His mother and sister by blood are lawful to his foster father and foster brother,” means that it is permissible for the child’s foster father or foster brother to marry the child’s mother or his sister by blood, because the nursling’s collateral relatives and ascendants have no connection to the foster relationship.

His statement, “Whoever is forbidden from marrying her daughter, if she nurses a girl, makes that girl forbidden to him as well,” means that any woman whose daughter is forbidden to marry you renders forbidden to you every girl whom she nurses. Thus, if his sister nurses a girl, that girl becomes forbidden to him, because his sister’s daughter is forbidden to him. This principle, which contains a degree of complexity, is sufficiently covered by the Prophet’s statement, peace and blessings be upon him: “What is prohibited through breastfeeding is what is prohibited through lineage.” (1)

It is well known that your sister—being the daughter of your mother—is forbidden to you. Thus, if your mother nurses a girl, that girl becomes your sister through breastfeeding. So adhere to the basic principles. It would have been better had the author not introduced this criterion, because it causes confusion. It is already known that whoever is forbidden from marrying her daughter is likewise forbidden from marrying any girl whom she has nursed.