31 – The Book of Suckling (Milk-Kinship)

A small quantity of suckling and a large quantity are the same: whenever the nursing takes place within the legally recognised period, it renders marriage unlawful.

According to Abu Ḥanifah, that period is thirty months; Abu Yusuf and Muḥammad say two years. Once the suckling period has elapsed, no prohibition arises from later nursing.

Whatever is forbidden through lineage is likewise forbidden through suckling, except in two cases: a man is permitted to marry the mother of his foster-sister, whereas he may not marry the mother of his biological sister; and he may marry the sister of his foster-son, whereas he may not marry the sister of his biological son. The wife of his foster-son is unlawful to him, just as the wife of his biological son is, and the wife of his foster-father is also unlawful to him, just as the wife of his biological father is.

The “milk of the sire” (laban al-faḥl) also establishes prohibition. This occurs when a woman breastfeeds a girl: that girl then becomes forbidden to the woman’s husband, to the husband’s fathers, and to his sons, and the husband from whose fluid the milk was produced becomes a foster-father to the child.

A man may marry the sister of his foster-brother just as he may marry the sister of his half-brother through lineage. For example, if a paternal half-brother has a maternal sister, that sister is lawful to his paternal brother.

Any two children who have suckled from the same breast may not marry one another. The wet nurse may not marry any child of the woman she has suckled, nor any of that child’s descendants; and the suckled boy may not marry the sister of the wet nurse’s husband, for she is his paternal aunt through suckling.

If milk is mixed with water and the milk predominates, the prohibition applies; but if the water predominates, it does not. If milk is mixed with food, no prohibition applies—even if the milk predominates—according to Abu Ḥanifah. If it is mixed with medicine and the milk predominates, the prohibition applies.

And if milk is expressed from a woman