´It was narrated that Yahya bin Husain said:` "I heard my grandmother say: 'I heard the Messenger of Allah say, during the Farewell Pilgrimage: If an Ethiopian slave is appointed over you who rules according to the Book of Allah, then listen to him and obey."'
Hadith Referenceسنن نسائي / كتاب البيعة / 4197
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:صحيح مسلم