It is narrated from Sayyiduna Abu Usayd (may Allah be pleased with him) that he said: The Messenger of Allah (peace and blessings be upon him) said: "The best of the Ansar are Banu al-Najjar, then Banu Abd al-Ashhal, then Banu Sa'idah, then Banu al-Harith bin al-Khazraj."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16639