Musnad Ahmad 25:184

Yahya ibn Abi Bukayr narrated to us, Isra'il narrated to us, from Simak ibn Harb, from 'Ikrimah, from Ibn 'Abbas, who said: It was said to the Messenger of Allah, may Allah bless him and grant him peace, when he finished from Badr: "The caravan is upon you; there is nothing [standing] between you and it." He said: So Al-'Abbas ibn 'Abd al-Muttalib called out to him: "It is not appropriate for you." He said: "And why?" He said: "Because Allah, the Almighty and Majestic, only promised you one of the two parties, and He has already given you what He promised you."