My foster-uncle Abu'l Ja'd (kunya of Aflah) sought permission from me, which I refused. (Hisham said to me that Abu'l-Ja'd was in fact Abu'l-Qu'ais). When Allah's Apostle (ﷺ) came, I ('A'isha) informed him about it. He said: Why did you not permit him? Let your right hand or hand be besmeared with dust.
Don't observe veil from him for he is Mahram (one with whom marriage cannot be contracted) on account of fosterage as one is Mahram on account of consanguinity.
Aflah b. Qu'ais sought permission from me (to enter the house), but I refused to grant him the permission, and he sent me (the message saying): I am your uncle (in the sense) that the wife of my brother has suckled you, (but still) I refused to grant him permission. There came the Messenger of Allah (ﷺ) and I made a mention of it to him, and he said: He can enter (your house), for he is your uncle.
Messenger of Allah, why is it that you select (your wife) from among the Quraish, but you ignore us (the nearest of the kin)? Thereupon he said: Have you anything for me (a suitable match for me)? I said; Yes, the daughter of Hamza, whereupon Allah's Messenger (ﷺ) said: She is not lawful for me, for she is the daughter of my brother by reason of fosterage.
It was proposed that he (the Holy Prophet) be married to the daughter of Hamza, whereupon he said: She is not lawful for me for she is the daughter of my foster-brother, and that is unlawful by reason of fosterage what is unlawful by reason of genealogy.
It was said to the Messenger of Allah (ﷺ): Is not the daughter of Hamza a suitable match for you? Or it was said: Why don't you propose to marry the daughter of Hamza, the son of Abd al-Muttalib? Thereupon he said: Hamza is my brother by reason of fosterage.
The Messenger of Allah (ﷺ) came to me and I said to him: Have you any inclination towards my the daughter of Abu Sufyan? He (the Holy Prophet) said: Then what should I do? I said: Marry her. He said: Do you like that? I said: I am not the exclusive (wife) of yours; I, therefore, wish to join my sister in good. He, said: She is not lawful for me. I said: I have been informed that you have given the proposal of marriage to Durrah daughter of Abu Salama He raid: You mean the daughter of Umm Salama? I said: Yes. He said: Even if she had not been my step-daughter brought up under my guardianship, she would not have been lawful for me, for she is the daughter of my foster-brother (Hamza), for Thuwaiba had suckled me and her father. So do not give me the proposal of the marriage of your daughters and sisters.