Musannaf Ibn Abi Shayba 9:1139

Ibn Numayr narrated to us, from Hisham ibn Urwah, from his father, from Zaynab bint Abi Salamah, from Umm Habibah, who said: "O Messenger of Allah, would you like to marry my sister, the daughter of Abu Sufyan?" He said: "She is not lawful for me." She said: "For it has reached me that you are proposing to Durrah bint Abi Salamah." He said: "The daughter of Abi Salamah?" She said: "Yes." He 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 breastfeeding. Thuwaybah nursed me and her father. So do not offer me your daughters nor your sisters."