Musnad Ahmad 1273:18

Ya'qub narrated to us, Ibn Akhi Ibn Shihab narrated to us, from his uncle, who said: 'Urwah ibn al-Zubayr informed me that Zaynab bint Abi Salamah informed him that Umm Habibah, the wife of the Prophet, may Allah bless him and grant him peace, informed her that she said to the Messenger of Allah, may Allah bless him and grant him peace: "O Messenger of Allah, marry my sister, the daughter of Abu Sufyan." She claimed that the Messenger of Allah, may Allah bless him and grant him peace, said to her: "Do you desire that?" She said: "Yes, O Messenger of Allah. I am not the only one for you, and the person I most love to share in my good is my sister." She said: The Messenger of Allah, may Allah bless him and grant him peace, said: "Indeed, that is not lawful for me." I said: "By Allah, O Messenger of Allah, we are talking about how you want to marry Durrah bint Abi Salamah." The Messenger of Allah, may Allah bless him and grant him peace, said: "The daughter of Umm Salamah?" She said: "Yes." The Messenger of Allah, may Allah bless him and grant him peace, said: "By Allah, even if she were not my stepdaughter under my guardianship, she would not be lawful for me. She is the daughter of my brother through nursing; Thuwaybah nursed me and Abu Salamah. So do not offer me your daughters, nor your sisters."