Once the Messenger of Allah (may Allah's peace and blessings be upon him) entered upon me while a man was in my house. He said: O ‘Ā'ishah, who is this (man)? I replied: He is my brother from breastfeeding. He said: O ‘Ā'ishah, be careful who you (women) count as your brothers from breastfeeding, for the breastfeeding (that makes marriage prohibited) is only that which satisfies hunger
The Messenger of Allah (may Allah's peace and blessings be upon him) said concerning the daughter of Hamzah: She is not lawful for me (to marry). That which is unlawful due to lineage (blood relation) is unlawful due to breastfeeding. She is the daughter of my foster-brother.
It was revealed in the Qur'an that: ten times of breastfeeding known with certainty establish prohibition (Mahram relationship through breastfeeding); then that was abrogated and replaced with five times of breastfeeding known with certainty. The Messenger of Allah (may Allah's peace and blessings be upon him) died while these (words of the abrogating verse) were still being recited as part of the Qur'an
No prohibition results from suckling, except for what penetrates the intestines from the breast before weaning
Even if she was not my stepdaughter whom I raised, she would still be unlawful for me because she is my niece through suckling. Thuwaybah breastfed me and Abu Salāmah (her father). So, do not offer me your daughters or sisters
Suckle him, and you will become unlawful for him (in marriage), and (the discomfort) which Abu Hudhayfah feels in his heart will disappear
