Musnad Abu Ya'la al-Mawsili 110:46

Abu Bakr ibn Abi Shaybah narrated to us, Abd al-Rahim narrated to us, from Isra'il, from Simak, from Ikrimah, from Ibn Abbas, who said: It was said, "O Messenger of Allah," when he finished from Badr, "You should take the caravan, for there is nothing beyond it." He said: So al-Abbas called out to him, "It is not appropriate." He said: So the Prophet, peace and blessings of Allah be upon him, said, "Why?" He said: "Because Allah promised you one of the two parties, and He has given you what He promised you."