Sayyidah Umm al-Husayn al-Ahmasiyyah (may Allah be pleased with her) narrates: I saw the Messenger of Allah (peace and blessings be upon him) during the Farewell Hajj on his mount, while Husayn was in my lap. He (peace and blessings be upon him) had passed his garment under his armpit, and he was saying: "O people, fear Allah, and listen and obey whoever is placed over you, even if he is a mutilated Abyssinian slave; still listen and obey, so long as he establishes among you the Book of Allah."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21840