Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) narrates: On the day of Badr the Prophet (peace and blessings be upon him) said: "Whoever among you is able should take the Banu Abd al-Muttalib captive (that is, not kill them), for they have been brought out by force."
Ahmad and al-Bazzar recorded it, and the narrators of Ahmad are thiqat (trustworthy).