Yahya · The Book on Government

If a slave is appointed over you and he conducts your affairs according to the Book of Allah, you should listen to him and obeey (his orders).

I heard her say: I performed Hajjat-ul-Wada' in the company of the Messenger of Allah (ﷺ). He said a lot of things (on this occasion). Then I heard him say: If a maimed slave is appointed a commander over you the narrator says: I think she said:" a black stave" who leads you according to the Book of Allah, then listen to him and obey him.