It has been narrated on the authority of Yahya bin Husain who learnt the tradition from his grandmother. Umm Husain. He said': I heard her say: I performed Hajjat-ul-Wada' in the company of the Messenger of Allah ( صلی اللہ علیہ وسلم ) . 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 slave" who leads you according to the Book of Allah, then listen to him and obey him.