Umm Habiba said, "Messenger of Allah, marry my sister, the daughter of Abu Sufyan."He asked, "Would you really like that?"She replied, "Yes. I am not your only wife, and I would love for my sister to share with me in any good."The Prophet ﷺ said, "That is not lawful for me."She said, "We have been told that you intend to marry the daughter of Abu Salama."He asked, "The daughter of Umm Salama?"She said, "Yes."He said, "Even if she were not my stepdaughter raised in my care, she would still not be lawful for me. She is the daughter of my brother through breastfeeding. Thuwayba nursed both me and Abu Salama. So do not offer me your daughters or your sisters."
يا رسول الله! انكح أختي بنت أبي سفيان. فقال: أو تحبين ذلك؟ فقلت: نعم، لست لك بمخلية. وأحب من شاركني في خير أختي. فقال النبي ﷺ: إن ذلك لا يحل لي قلت: فإنا نحدث أنك تريد أن تنكح بنت أبي سلمة. قال: بنت أم سلمة؟ قلت: نعم، فقال: 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 (5101) and Muslim in the Book of Breastfeeding (16:1449), both from the hadith of Zuhri, who said, Urwa bin Zubayr informed me, that Zaynab bint Abu Salama informed him, that Umm Habiba bint Abu Sufyan informed her, and he related it, the wording being Bukhari's. Muslim's wording is similar.In other reports, Thuwayba breastfed the Prophet ﷺ before Halima Sadiya did, as well as Hamza and Abu Salama, so these became his brothers through breastfeeding. Thuwayba was the freed slave of Abu Lahab, who freed her after the Prophet's ﷺ migration to Madinah. She died after the conquest of Khaybar. The Messenger of Allah ﷺ used to send her gifts of clothing and maintain ties with her. After her death, the Messenger of Allah ﷺ asked about her son Masruh, and he was told that he had also died. He then asked about her relatives, and he was told that none of them remained. I do not know whether she accepted Islam or not, and Ibn Abdul-Barr did not mention her in al-Istiab.