Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: Abdullah bin Mas'ud (may Allah be pleased with him) reached Abu Jahl on the day of Badr while he lay mortally wounded but still alive. He drew his sword and struck his neck, and his head flew off. Then he took his belongings, came to the Prophet (peace and blessings be upon him), and told him that he had killed Abu Jahl. He (peace and blessings be upon him) made him swear by Allah three times, and he swore; so he (peace and blessings be upon him) gave him the belongings.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12071