Volume 6 · Book 60 · Hadith 168
Narrated Said bin Jubair: I asked Ibn 'Abbas regarding Surat-al-Anfal. He said, "It was revealed in connection with the Battle of Badr."
— Sahih Bukhari, Volume 6, Book 60: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)), Hadith #168