Musnad Ahmad 266:4

Waki' narrated to us, he said: Sufyan narrated to us, from Abu al-Zinad, from Abu Salamah, from Abu Usayd, he said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "The best 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 of the Ansar there is good."