Musnad Abu Ya'la al-Mawsili 162:7

Yahya ibn Ayyub narrated to us, Ismail ibn Ja'far narrated to us, Muhammad ibn Abi Harmalah narrated to us, from Kurayb, the freed slave of Ibn Abbas, that Usamah ibn Zayd was riding behind the Messenger of Allah (may Allah bless him and grant him peace) from Arafat. When the Messenger of Allah (may Allah bless him and grant him peace) reached the mountain pass of al-Aysar, which is before Muzdalifah, he made the camel kneel. He said: Then he came, and I poured water for him for ablution, so he performed ablution. I said: "The prayer, O Messenger of Allah?" He said: "The prayer is ahead of you." So the Messenger of Allah (may Allah bless him and grant him peace) rode until he reached Muzdalifah, and he prayed. Then al-Fadl rode behind the Messenger of Allah (may Allah bless him and grant him peace) on the morning of Jam' (Muzdalifah).