As for the scope of this ruling, it involves three persons: the nursing woman, the man to whom the milk is attributed—her husband or master—and the nursling. Each of these three has ascendants, descendants, and collateral relatives. The nursing woman’s ascendants are her fathers and mothers, however far back they extend; her descendants are her sons and daughters, however far down they extend; and her collateral relatives are her siblings and her paternal and maternal aunts and uncles. The same applies to the man to whom the milk is attributed: he has ascendants, descendants, and collateral relatives. The nursling likewise has ascendants, descendants, and collateral relatives.

Breastfeeding does not affect the nursling’s ascendants or collateral relatives; rather, the ruling of breastfeeding pertains only to the nursling and his descendants. With regard to the nursing woman, it pertains to her ascendants, descendants, and collateral relatives; and with regard to the man to whom the milk is attributed, it pertains to his ascendants, descendants, and collateral relatives. This is a comprehensive division that makes it easy for a person to understand the effect of breastfeeding.

Let me give an example. Zayd nursed from Hind, whose husband was named Khalid. The ruling of breastfeeding applies to Hind’s mothers and grandmothers, because they are her ascendants; to Hind’s daughters, because they are her descendants; and likewise to Hind’s sisters and her paternal and maternal aunts. With respect to the man to whom the milk is attributed—Khalid—the ruling applies to his mothers and grandmothers, because they are his ascendants; to his daughters, because they are his descendants; and to his brothers, because they are his collateral relatives.

There remains the nursling, Zayd: the ruling of breastfeeding applies to his offspring, but not to his ascendants or collateral relatives. Thus, the nursling’s brother may marry the woman who nursed his brother, because breastfeeding does not affect the nursling’s collateral relatives. Likewise, the nursling’s father may marry the woman who nursed his son, because breastfeeding does not affect the nursling’s ascendants. But the nursling’s son may not marry the nursling’s foster sister through the woman who breastfed him, because he is among the nursling’s descendants, and breastfeeding affects the nursling’s descendants.