The Prophet 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."

A hadith like this is narrated on the authority of Hammam, Sa'id, Bishr b 'Umar, but with a small variation of words.

My foster uncle came and asked permission (to enter) but I refused to admit him till I asked Allah's Apostle about that. He said, "He is your uncle, so allow him to come in." I said, "O Allah's Apostle! I have been suckled by a woman and not by a man." Allah's Apostle said, "He is your uncle, so let him enter upon you." And that happened after the order of Al-Hijab (compulsory veiling) was revealed. All things which become unlawful because of blood relations are unlawful because of the corresponding foster suckling relations.

Yahya related to me from Malik from Ibn Shihab that he said, "Suckling however little or much, makes haram. Kinship by suckling makes men mahram."

Yahya said that he had heard Malik say, "Suckling, however little or much when it is in the first two years, makes haram. As for what is after the first two years, little or much, it does not make anything haram. It is like food."

Allah, the brother of Abu Al-Qu'ais asked my permission to enter after the verses of Al-Hijab (veiling the ladies) was revealed, and I said, "By Allah, I will not admit him unless I take permission of Allah's Apostle for it was not the brother of Al-Qu'ais who had suckled me, but it was the wife of Al-Qu'ais, who had suckled me." Then Allah's Apostle entered upon me, and I said, "O Allah's Apostle! The man has not nursed me but his wife has nursed me." He said, "Admit him because he is your uncle (not from blood relation, but because you have been nursed by his wife), Taribat Yaminuki." `Urwa said, "Because of this reason, ' Aisha used to say: Foster suckling relations render all those things (marriages etc.) illegal which are illegal because of the corresponding blood relations." (See Hadith No. 36, Vol. 7)

Yahya related to me from Malik from Hisham ibn Urwa from his father that A'isha, umm al-muminin said, "My paternal uncle by suckling came to me and I refused to give him permission to enter until I had asked the Messenger of Allah, may Allah bless him and grant him peace, about it. The Messenger of Allah, may Allah bless him and grant him peace, came and I asked him about it. He said, 'He is your paternal uncle, so give him permission.' So I said, 'Messenger of Allah! The woman nursed me not the man.' He said, 'He is your paternal uncle, so let him enter.' "

A'isha said, "That was after the veil had been imposed on us."

A'isha added, "What is haram by birth is made haram by suckling."

The Prophet forbade that a woman should be married to a man along with her paternal aunt or with her maternal aunt (at the same time). Az-Zuhri (the sub-narrator) said: There is a similar order for the paternal aunt of the father of one's wife, for 'Urwa told me that `Aisha said, "What is unlawful because of blood relations, is also unlawful because of the corresponding foster suckling relations."

The Prophet (saws) said: What is unlawful by reason of consanguinity is unlawful by reason of fosterage.

Yahya related to me from Malik from Abdullah ibn Dinar from Sulayman ibn Yasar and from Urwa ibn az-Zubayr from A'isha umm al- muminin, that the Messenger of Allah, may Allah bless him and grant him peace, said, " What is haram by birth is haram by suckling."