Musnad Ahmad 5:93

Waki’ narrated to us, Isra’il narrated to us, from Abu Ishaq, from Harithah ibn Mudarrib, from Ali, who said: "We saw ourselves on the day of Badr, and we were seeking refuge with the Messenger of Allah, may Allah bless him and grant him peace, and he was the closest of us to the enemy. And he was among the most intense of the people in might on that day."