Sayyiduna Abu al-Yasar (may Allah be pleased with him) said: On the day of Badr I looked at al-Abbas bin Abd al-Muttalib; he was standing like an idol, and tears were flowing from his eyes. When I looked at him, I said: "May Allah give you an evil recompense for your kinship! Are you fighting against your nephew alongside his enemy?" He said: "What happened? Has he been killed?" I said: "Allah is mightier and a greater helper for him than that." He said: "What do you want from me?" I said: "To take you captive, for the Messenger of Allah (peace and blessings be upon him) has forbidden killing you." He said: "I am not the first captive." So I took him captive and then brought him to the Messenger of Allah (peace and blessings be upon him).
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16419