Musannaf Ibn Abi Shayba 36:199

Waki’ narrated to us, from al-Rabi’, from al-Hasan, regarding [the verse]: "And whoever turns his back to them on such a day, unless it be for tactical maneuvering for battle or to join a company," he said: "This is specifically for the day of Badr; fleeing from the battlefield is not among the major sins."