سنن النسائي

It was narrated from Zainab bint Abi Salamah that Umm Habibah, the wife of the Prophet (ﷺ) said: "O Messenger of Allah, marry the daughter of my father" - meaning her sister. The Messenger of Allah (ﷺ) said: "Would you like that?" She said: "Yes; I do not have you all to myself, and I would like to share this goodness with my sister." The Prophet (ﷺ) said: "That is not permissible for me." Umm Habibah said: "O Messenger of Allah, by Allah, we have been saying that you want to marry Durrah bint Abi Salamah." He said: "The daughter of Umm Salamah?" I said: "Yes." He said: "By Allah, even if she were not my stepdaughter who is in my care, she would not be permissible for me (to marry), because she is the daughter of my brother through breast-feeding. Thuwaibah breastfed Abu Salamah and I. So do not offer your daughters or sisters to me in marriage."