Musnad Ahmad 1243:0

Narrated by Umm al-Husayn al-Ahmasiyyah: I performed the Hajj of Farewell with the Messenger of Allah (peace and blessings of Allah be upon him). I saw him when he threw the pebbles at the Jamrah and then departed, and with him was Bilal and Usamah. One of them was holding the bridle of the she-camel of the Messenger of Allah (peace and blessings of Allah be upon him), and the other was raising his garment over the head of the Messenger of Allah (peace and blessings of Allah be upon him) to shade him from the sun. The Messenger of Allah (peace and blessings of Allah be upon him) spoke some words between the time he threw the pebbles at the Jamrah and the time he departed. I heard him say: "If a slave is appointed over you who leads you according to the Book of Allah, then listen to him and obey him."