Musnad Ahmad 266:1

Hajjaj narrated to us, he said: Shu'bah narrated to me, he said: I heard Qatadah, from Anas ibn Malik, from Abu Usayd al-Sa'idi. Abdullah ibn Ahmad said: My father said: And Ibn Ja'far said: From Abu Usayd, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The best of the houses of the Ansar are the Banu al-Najjar, then the Banu 'Abd al-Ashhal, then the Banu al-Harith ibn al-Khazraj, then the Banu Sa'idah; and in all the houses of the Ansar there is good." Sa'd ibn 'Ubadah said: "I do not see the Messenger of Allah (peace and blessings of Allah be upon him) except that he has favored others over us." It was said: "He has favored you over many."