Musnad Abu Ya'la al-Mawsili 3:42

Ubayd Allah narrated to us, Hisham ibn Abd al-Malik narrated to us, Zuhayr ibn Mu'awiyah narrated to us, Abu Ishaq narrated to me, from Harithah ibn Mudarrib, from Ali, that he said: When the intensity of battle reddened and the people met [in combat], we would protect ourselves with the Messenger of Allah, peace and blessings of Allah be upon him. There was no one among us closer to the enemy than him.