It is narrated from Sayyida Aisha (may Allah be pleased with her), she says: The Noble Prophet (peace and blessings be upon him) was sitting with me when I heard the voice of a man who was seeking permission to enter the house of Sayyida Hafsa (may Allah be pleased with her). I said: O Messenger of Allah! This man is seeking permission to enter your house? The Messenger of Allah (peace and blessings be upon him) said: I think he is such-and-such foster uncle of Hafsa. I said: O Messenger of Allah! If my such-and-such foster uncle were alive, could he enter upon me? The Messenger of Allah (peace and blessings be upon him) said: Yes, absolutely, indeed fosterage makes unlawful those relationships which are made unlawful by lineage and birth.
Hadith Takhrij«أخرجه البخاري: 2646، 3105، ومسلم: 1444 ، (انظر مسند أحمد ترقيم الرسالة: 25453 ترقیم بيت الأفكار الدولية: 25967»
Brief Explanation
Benefits: … Just as the prohibition (hurmah) of women is established due to suckling (rada‘ah), similarly, if the one who is suckled is a girl, she too will become prohibited (haram) to certain men due to suckling. If the woman who breastfeeds is the foster (rada‘i) mother, then her husband will be the foster father, her son will be the foster brother, her brother will be the foster maternal uncle, her father will be the foster maternal grandfather, and the parents of the foster father will be the foster paternal grandfather and grandmother. Likewise, by analogy, the sequence of uterine and consanguineous foster siblings will also be established.
The reason for this is that a woman’s milk descends as a result of her husband’s intercourse and pregnancy; thus, the husband also has a share in the woman’s milk. Therefore, the relationship of the child (boy or girl) who is breastfed will be established with both the woman and her husband.