Sahih Bukhari
Sahih Bukhari Volume 009, Book 089, Hadith Number 256.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 89. Judgments (Ahkaam)
Narrated By Anas bin Malik : Allah's Apostle said, "You should listen to and obey, your ruler even if he was an Ethiopian (black) slave whose head looks like a raisin."