Musnad Ahmad 1005:1

Husayn ibn Muhammad narrated to us, Jarir—meaning Ibn Hazim—narrated to us, from Muhammad ibn Ishaq, from Dawud ibn Husayn, from Abd al-Rahman ibn Abi Aqabah, from Abu Aqabah, who was a freed slave from the people of Persia, who said: I witnessed the day of Uhud with the Prophet of Allah, may Allah bless him and grant him peace. I struck a man from the polytheists and said: "Take it from me, and I am the Persian youth." This reached the Prophet, may Allah bless him and grant him peace, and he said: "Why did you not say: 'Take it from me, and I am the Ansar youth'?"