Sahih Bukhari Volume 007, Book 064, Hadith Number 285.
Narrated By Um Habiba: (The wife of the Prophet) I said, "O Allah's Apostle! Will you marry my sister, the daughter of Abu Sufyan." The Prophet said, "Do you like that?" I said, "Yes, for I am not your only wife, and the person I like most to share the good with me, is my sister." He said, "That is not lawful for me." I said, "O Allah's Apostle! We have heard that you want to marry Durra, the daughter of Abu Salama." He said, "You mean the daughter of Um Salama?" I said, "Yes." He said, "Even if she were not my step-daughter, she is unlawful for me, for she is my foster niece. Thuwaiba suckled me and Abu Salama. So you should not present to me your daughters and sisters."
Narrated 'Ursa: Thuwaiba had been a slave girl whom Abu Lahab had emancipated.