Musnad Ahmad 25:211

Asbat narrated to us, Abu Ishaq al-Shaybani narrated to us, from Hammad, from Ibrahim, from Ibn Abbas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If you send the dog and it eats from the game, then do not eat, for it only caught it for itself. And if you send it and it kills but does not eat, then eat, for it only caught it for its owner." Abdullah said: It was in my father’s book: "From Ibrahim, he said: I heard Ibn Abbas," but my father struck through it. That is how Asbat said it.