She narrated that she said to the Messenger of Allah ﷺ, "Messenger of Allah, marry my sister Azza."The Messenger of Allah ﷺ asked, "Would you really like that?"She replied, "Yes, Messenger of Allah. I am not your only wife, and I would love for my sister to share with me in any good."The Messenger of Allah ﷺ said, "But that is not lawful for me."She said, I then said, "Messenger of Allah, we have been hearing that you intend to marry Durra, the daughter of Abu Salama."He asked, "The daughter of Abu Salama?"She answered, "Yes."The Messenger of Allah ﷺ said, "Even if she were not my stepdaughter under my care, she would still not be lawful for me. She is the daughter of my brother through nursing. Thuwayba nursed both me and Abu Salama. So do not present your daughters or your sisters to me for marriage."
حدثتها أنها قالت لرسول الله ﷺ يا رسول الله! انكح أختي عزة. فقال رسول الله ﷺ: أتحبين ذلك؟ فقالت: نعم. يا رسول الله! لست لك بمخلية. وأحب من شركني في خير أختي! فقال رسول الله ﷺ: فإن ذلك لا يحل لي قالت: فقلت: يا رسول الله! فإنا نتحدث أنك تريد أن تنكح درة بنت أبي سلمة. قال: بنت أبي سلمة؟ قالت: نعم. قال رسول الله ﷺ: لو أنها لم تكن ربيبتي في حجري ما حلت لي. إنها ابنة أخي من الرضاعة، أرضعتني وأبا سلمة ثويبة. فلا تعرضن علي بناتكن ولا أخواتكن.
Bukhari narrated it in the Book of Marriage (5107), and Muslim narrated it in the Book of Breastfeeding (16:1449), both through Muhammad bin Shihab Zuhri, that Urwa informed him that Zaynab bint Abu Salama informed him that Umm Habiba said, and then he mentioned it.In other reports, Hamza was also among those breastfed by Thuwayba. This made the Prophet ﷺ, Abu Salama, and Hamza brothers through breastfeeding.As for his saying, "my stepdaughter under my care," the word for "care" (hijr) can be read with a fatha or a kasra on the ha. In this there is an argument for Dawud Zahiri, that a stepdaughter is not forbidden in marriage unless she was under the care of her mother's husband, based on the words of Allah, "And your stepdaughters who are under your care from your wives with whom you have consummated marriage" [Nisa 4:23]. If she was not under his care, then she would be permissible for him.The position of the scholars generally, other than Dawud, is that she is forbidden regardless of whether she was under his care or not. When a qualification is mentioned because it reflects the most common case, it does not carry a restrictive meaning that must be acted upon. A similar example is the words of Allah, "And do not kill your children out of poverty" [Anaam 6:151], though it is well known that killing is forbidden for other reasons as well. The qualification "out of poverty" was mentioned only because it was the most common case. There are many similar examples in the Quran.This point was made by Nawawi in his commentary on Sahih Muslim.