Musnad Ahmad 1243:11

'Affan narrated to us, he said: Shu'bah narrated to us, he said: Yahya ibn al-Husayn narrated to us, he informed me that he heard his grandmother say: I heard the Messenger of Allah, peace and blessings of Allah be upon him, delivering a sermon at 'Arafat, and he was saying: "Even if a slave is appointed over you who leads you by the Book of Allah, then listen to him and obey him." 'Abdullah said: And I heard my father say: I indeed see for him [the ruler] listening and obedience in hardship and ease, and in what is desired and what is disliked.