Musnad Ahmad 266:3

'Abd al-Razzaq informed us, he said: Sufyan narrated to us, from 'Abd Allah ibn Dhakwan, from Abu Salamah, from Abu Usayd al-Sa'idi, from the Prophet, peace and blessings of Allah be upon him: "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." Then he said: "And in all the houses of the Ansar there is good." Sa'd ibn 'Ubadah said: "We have been made the fourth of four; saddle my donkey for me." His nephew said to him: "Do you wish to refute the Messenger of Allah, peace and blessings of Allah be upon him? It is sufficient for you that you are the fourth of four."