Musnad Ahmad 25:1245

Bakr ibn Isa Abu Bishr al-Rasibi narrated to us, Abu 'Awanah narrated to us, from Abu Hamzah, who said: I heard Ibn Abbas saying: I was a young boy running with the boys, and I turned around, and there was the Prophet of Allah, may Allah bless him and grant him peace, behind me, approaching. I said: The Prophet of Allah, may Allah bless him and grant him peace, has not come except for me. He said: So I ran to hide behind the door of a house. He said: I did not realize until he reached me and took hold of the back of my neck, and he gave me a light slap. Then he said: "Go and call Mu'awiyah for me." He said: And he was his scribe. So I ran and came to Mu'awiyah and said: Answer the Prophet of Allah, may Allah bless him and grant him peace, for he has a need.