Musnad Ahmad 2:310

Ishaq ibn Isa narrated to us, Malik informed me, from Yahya ibn Said, that he heard Anas ibn Malik saying: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Shall I not inform you of the best of the houses of the Ansar? Banu al-Najjar, then Banu Abd al-Ashhal, then Banu al-Harith ibn al-Khazraj, then Banu Sa'idah." And he said: "In all the houses of the Ansar there is good."