Musnad Ahmad 5:59

Abu Mu'awiyah narrated to us, from al-A'mash, from Sa'd ibn 'Ubaydah, from Abu 'Abd al-Rahman al-Sulami, from 'Ali, who said: I said: "O Messenger of Allah, why do you choose [a wife] from Quraysh and leave us?" He said: "And do you have anyone?" I said: "Yes, the daughter of Hamzah." He said: "She is not lawful for me; she is the daughter of my brother through breastfeeding."