Narrated `Aisha: (the wife of the Prophet) that while Allah's Apostle was with her, she heard a voice of a man asking permission to enter the house of Hafsa. `Aisha added: I said, "O Allah's Apostle! This man is asking permission to enter your house." The Prophet said, "I think he is so-and-so," naming the foster-uncle of Hafsa. `Aisha said, "If so-and-so," naming her foster uncle, "were living, could he enter upon me?" The Prophet said, "Yes, for foster suckling relations make all those things unlawful which are unlawful through corresponding birth (blood) relations."

Narrated Ibn `Abbas: It was said to the Prophet, "Won't you marry the daughter of Hamza?" He said, "She is my foster niece (brother's daughter). "

Narrated Um Habiba: (daughter of Abu Sufyan) I said, "O Allah's Apostle! Marry my sister. the daughter of Abu Sufyan." The Prophet said, "Do you like that?" I replied, "Yes, for even now I am not your only wife and I like that my sister should share the good with me." The Prophet said, "But that is not lawful for me." I said, We have heard that you want to marry the daughter of Abu Salama." He said, "(You mean) the daughter of Um Salama?" I said, "Yes." He said, "Even if she were not my step-daughter, she would be unlawful for me to marry as she is my foster niece. I and Abu Salama were suckled by Thuwaiba. So you should not present to me your daughters or your sisters (in marriage)." Narrated 'Urwa:Thuwaiba was the freed slave girl of Abu Lahb whom he had manumitted, and then she suckled the Prophet. When Abu Lahb died, one of his relatives saw him in a dream in a very bad state and asked him, "What have you encountered?" Abu Lahb said, "I have not found any rest since I left you, except that I have been given water to drink in this (the space between his thumb and other fingers) and that is because of my manumitting Thuwaiba."