It was said to the Messenger of Allah (ﷺ): Is not the daughter of Hamza a suitable match for you? Or it was said: Why don't you propose to marry the daughter of Hamza, the son of Abd al-Muttalib? Thereupon he said: Hamza is my brother by reason of fosterage.
Sahih Muslim Book 17, Hadith 18
← Previous Hadith A hadith like this is narrated on the authority of Hammam, Sa'id, Bishr b 'Umar, but with a small variation of words.

Sahih Muslim Book 17, Hadith 17 Next Hadith → The Messenger of Allah (ﷺ) came to me and I said to him: Have you any inclination towards my the daughter of Abu Sufyan? He (the Holy Prophet) said: Then what should I do? I said: Marry her. He said: Do you like that? I said: I am not the exclusive (wife) of yours; I, therefore, wish to join my sister in good. He, said: She is not lawful for me. I said: I have been informed that you have given the proposal of marriage to Durrah daughter of Abu Salama He raid: You mean the daughter of Umm Salama? I said: Yes. He said: Even if she had not been my step-daughter brought up under my guardianship, she would not have been lawful for me, for she is the daughter of my foster-brother (Hamza), for Thuwaiba had suckled me and her father. So do not give me the proposal of the marriage of your daughters and sisters.

Sahih Muslim Book 17, Hadith 19