Musnad Abu Ya'la al-Mawsili 135:1

Abu Bakr ibn Abi Shaybah narrated to us, 'Abdah narrated to us, from 'Asim al-Ahwal, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) established a pact of brotherhood between the Quraysh and the Ansar in my house which is in Medina.