Narrated Aisha
Aflah asked the permission to visit me but I did not allow him. He said, "Do you veil yourself before me although I am your uncle?" `Aisha said, "How is that?" Aflah replied, "You were suckled by my brother's wife with my brother's milk." I asked Allah's Messenger (ﷺ) about it, and he said, "Aflah is right, so permit him to visit you."
Narrated Ibn `Abbas
The Prophet (ﷺ) said about Hamza's daughter, "I am not legally permitted to marry her, as foster relations are treated like blood relations (in marital affairs). She is the daughter of my foster brother."
Narrated `Amra bint `Abdur-Rahman
That `Aisha the wife of the Prophet (ﷺ) told her uncle that once, while the Prophet (ﷺ) was in her house, she heard a man asking Hafsa's permission to enter her house. `Aisha said, "I said, 'O Allah's Messenger (ﷺ)! I think the man is Hafsa's foster uncle.' " `Aisha added, "O Allah's Messenger (ﷺ)! There is a man asking the permission to enter your house." Allah's Messenger (ﷺ) replied, "I think the man is Hafsa's foster uncle." `Aisha said, "If so-and-so were living (i.e. her foster uncle) would he be allowed to visit me?" Allah's Apostle said, "Yes, he would, as the foster relations are treated like blood relations (in marital affairs).
Narrated Aisha
Once the Prophet (ﷺ) came to me while a man was in my house. He said, "O `Aisha! Who is this (man)?" I replied, "My foster brothers" He said, "O `Aisha! Be sure about your foster brothers, as fostership is only valid if it takes place in the suckling period (before two years of age).