Al-Matalib al-'Aliyah 4248 — The Battle of Badr

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that Allah Almighty had initially made it obligatory upon the Muslims that one of them should fight against ten (of the enemy), but this command weighed very heavily and was difficult for them. So Allah Almighty lightened it for them, reducing this burden and setting the limit that one man should fight against two. On this occasion Allah Almighty revealed this verse: "If there are twenty steadfast among you, they will overcome two hundred" [Surah al-Anfal: 65]. Then Allah Almighty said: "Had it not been for a decree from Allah that preceded, there would have touched you, for what (ransom) you took, a great punishment" [Surah al-Anfal: 68]; this refers to the spoils of the Battle of Badr, and the meaning of Allah Almighty's words is: "I do not punish anyone who has disobeyed Me until I have first warned him." Then Allah Almighty said: "O Prophet, say to those of the captives who are in your hands" [Surah al-Anfal: 70] (to the end of the verse). Sayyiduna al-Abbas (may Allah be pleased with him) said: By Allah, this verse was revealed about me; when I informed the Messenger of Allah (peace and blessings be upon him) of my acceptance of Islam and asked him (peace and blessings be upon him) to take into account the twenty uqiyah of gold that had been taken from me (as ransom), Allah Almighty gave me in return twenty slaves, each of whom has abundant wealth in his hands for trade; and along with this worldly reward, I have complete hope for the forgiveness and pardon of Allah Almighty.
This chain is sahih (authentic). Ibn Marduyah narrated it in the same way in his al-Tafsir al-Musnad from Ahmad bin al-Husayn, from Abdullah bin Muhammad, from Ishaq; and Imam al-Tabarani recorded it from the hadith of Yazid bin Harun, from Ibn Ishaq.