Sahih Bukhari Volume 6, Book 60, Hadith Number 410.

Narrated By ‘Umar : I recommend that my successor should take care of and secure the rights of the early emigrants; and I also advise my successor to be kind to tzhe Ansar who had homes (in Medina) and had adopted the Faith, before the Prophet migrated to them, and to accept the good from their good ones and excuse their wrong doers.