Sahih Bukhari
Merits of the Helpers in Madinah (Ansaar)
Volume: 005 / Book Number: 058 / Hadith Number: 134
Narrated Abu Usaid:
That he heard the Prophet saying, "The best of the Ansar, or the best of the Ansar families (homes) are Banu An-Najjar, Bani 'Abdul Ash-hal, Banu Al-Harith and Banu Sai'da."