Musnad Ahmad 5:535

'Abdullah narrated to us, Muhammad ibn 'Abdullah ibn Numayr narrated to me, my father narrated to us, al-A'mash narrated to us, from Sa'd ibn 'Ubaydah, from Abu 'Abd al-Rahman, from 'Ali, who said: I said: "O Messenger of Allah, why do I see you showing preference to Quraysh and leaving us?" He said: "Do you have anything?" I said: "The daughter of Hamzah." He said: "She is the daughter of my brother through breastfeeding."