consensus. The line of reasoning for the first opinion is that the prohibition between them is a derivative of the prohibition of paternity. Since the prohibition of paternity is not established (31), that which is a derivative of it is also not established. This differs from the prohibition regarding one's daughter from adultery, because she is truly from his sperm, unlike in our case. It also differs from the prohibition of affinity (musaharah), for the prohibition there does not depend on the establishment of lineage; therefore, one's mother-in-law and step-daughter are prohibited [to him] without [the existence of] a blood relationship. However, the prohibition of breastfeeding is built upon lineage, which is why he (peace and blessings of Allah be upon him) said: "Breastfeeding prohibits what lineage prohibits" (32). As for the nursing woman, the breastfed child is prohibited to her and is attributed to her according to everyone. Likewise, all of her children and her relatives who are prohibited to her children are prohibited to this breastfed child, just as in the case of breastfeeding with permissible milk (33). If the breastfed child is a girl, she is prohibited to the one who performed the li'an (imprecation) without disagreement as well, because she is his step-daughter, being the daughter of his wife through breastfeeding. She is also prohibited to the adulterer, according to those who hold the view that affinity establishes prohibition, and similarly, her daughters and the daughters of the breastfed boy are prohibited for that same reason.

Section: If two men have intercourse with a woman and she gives birth to a child, and she breastfeeds a child with [the milk resulting from] that pregnancy, that child becomes the son of whichever man the lineage (34) of the born child is established from, regardless of whether his lineage is established through physiognomy (qafah) or otherwise. If the physiognomists attribute him to both, then the breastfed child becomes the son of both. Thus, in every case, the breastfed child follows the one related by blood; whenever the blood relative is joined to a person, the breastfed child is the same. If the blood relative is denied from one of them, the breastfed child is the same, because he was breastfed by his milk, and his prohibition is a derivative of his prohibition. If his lineage is not established from either of them due to the inability to use physiognomy, [or his similarity] (35) to them, or similar reasons, he is prohibited to both, giving precedence to the prohibition (al-hazr). This is because it is possible that he is the son of both, or it is possible that he is the son of (36) one of them; thus, his relatives are prohibited to him while the relatives of the other are not, and his sister has become mixed with another, so all are prohibited, just as if he knew his sister specifically, then...