Musnad Abu Ya'la al-Mawsili 3:294

'Abd al-Rahman ibn Salih narrated to us, Yahya ibn Adam narrated to us, from Isra'il, from Abu Ishaq, from Hubayrah ibn Yarim and Hani' ibn Hani', from 'Ali, who said: The Messenger of Allah (may Allah bless him and grant him peace) said to Zayd ibn Harithah when they disputed over the daughter of Hamzah: "As for you, O Zayd, you are our brother and our freedman (mawla)."