It is narrated from Abdullah bin Abbas (may Allah be pleased with them both) that the daughter of Hamzah (may Allah be pleased with him) was proposed for the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "She is not lawful for me, for she is the daughter of my foster brother, and Allah Almighty has made unlawful through suckling all that He has made unlawful through lineage." In the narration of Hudbah: "She is not suitable for me, for she is the daughter of my foster brother, and what is unlawful through lineage is also unlawful through suckling."
Bukhari narrated it in the Sahih from Muslim bin Ibrahim, and Muslim narrated it from Hudbah bin Khalid.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرضاع / 15612