Musnad Ahmad 774:15

Hushaym narrated to us, Mujalid informed us, from al-Sha'bi, from 'Adi ibn Hatim, who said: I asked the Messenger of Allah (peace and blessings of Allah be upon him) about hunting with a dog. He said: "If you send your trained dog and mention the name of Allah over it, and it catches [the prey], and you reach it while it is still alive, then slaughter it. But if it killed it, then eat [it]. However, if it has eaten from it, then do not eat."