Sahih al-Bukhari Book 70, Hadith 1
The Prophet (ﷺ) said, "Give food to the hungry, pay a visit to the sick and release (set free) the one in
captivity (by paying his ransom).
(the wife of the Prophet) I said, "O Allah's Messenger (ﷺ)! Will you marry my sister, the daughter of Abu Sufyan." The Prophet (ﷺ) 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 Messenger (ﷺ)! 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 stepdaughter, 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 'Urwa: Thuwaiba had been a slave girl whom Abu Lahab had emancipated.
The family of Muhammad did not eat their fill for three successive days till he died.