Musannaf Ibn Abi Shayba 36:148

Al-Fadl ibn Dukayn narrated to us, he said: Yunus ibn Abi Ishaq narrated to us, from al-Aizar ibn Hurayth, who said: The herald of the Messenger of Allah, may Allah bless him and grant him peace, called out on the day of Badr: "There is no security for anyone among the people," meaning [the enemy], "except for Abu al-Bakhtari. So whoever has captured him, let him release him, for the Messenger of Allah, may Allah bless him and grant him peace, has granted him security." Then they found that he had been killed.