Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) says: When this verse was revealed: "Soon the assembly (or band) will be defeated, and they will turn their backs and flee," I thought: "Which band could be meant by this?" When the Battle of Badr came, I saw the Prophet (peace and blessings be upon him) brandishing a sword in his hand, and he was reciting this verse: "Soon the assembly (or band) will be defeated, and they will turn their backs and flee."
Al-Tabarani recorded it in al-Mu'jam al-Awsat. Its chain contains Muhammad bin Isma'il bin Ali al-Ansari, and I do not know him.