It was narrated from Ibn 'Abbas:
that the Messenger of was offered the daughter of Hamzah bin 'Abdul-Muttalib in marriage, and he said: "She is the daughter of my brother through breastfeeding, and breastfeeding makes unlawful (for marriage) the same things that blood ties make unlawful." (ID)
English reference (ID): Vol. 3, Book 9, Hadith 1938 (ID)
Arabic reference (ID): Book 9, Hadith 2013 (ID)