Musnad Ahmad 264:1

Aswad ibn Amir narrated to us, he said: Muslim ibn Khalid narrated to us, from Amr ibn Yahya al-Mazini, from his father, from Shuqran, the freed slave of the Messenger of Allah, may Allah bless him and grant him peace, who said: I saw him—meaning the Prophet, may Allah bless him and grant him peace—heading toward Khaybar on a donkey, praying upon it, gesturing with a gesture.