Musnad Ahmad 627:26

Muhammad ibn Fudayl narrated to us, from Bayan, from al-Sha'bi, from 'Adi ibn Hatim, who said: I asked the Messenger of Allah (peace and blessings of Allah be upon him) and said: "We are a people who hunt with these dogs." He said: "If you send your trained dogs and mention the name of Allah, then eat from what they catch for you, even if it killed it. Unless the dog has eaten from it, for if it has eaten, do not eat, for I fear that it only caught it for itself. And if other dogs have mixed with them, then do not eat."