Musannaf Ibn Abi Shayba 9:1136

Ali ibn Mushir narrated to us, from Sa'id, from Qatadah, from Jabir ibn Zayd, from Ibn Abbas, that the Messenger of Allah (may Allah bless him and grant him peace) was asked for the hand of the daughter of Hamza ibn Abd al-Muttalib. He said: "She is the daughter of my brother through breastfeeding, and indeed, that which is forbidden through lineage is forbidden through breastfeeding."