Musnad Ahmad 1243:5

Yahya ibn Sa'id narrated to us, from Shu'bah, who said: Yahya ibn al-Husayn ibn 'Urwah narrated to us, he said: My grandmother narrated to me, she said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Even if a slave is appointed over you who leads you by the Book of Allah the Almighty, then listen to him and obey him."