Allah, exalted be His praise, says: "They ask you what has been made lawful for them. Say: Good and pure things have been made lawful for you, and also the hunting animals that you have trained to chase game; you teach them of what Allah has taught you (of knowledge). So eat of what (game) they hold for you." [Surah al-Ma'idah: 4]
Sayyiduna Abu Rafi' (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) ordered us to kill dogs. The people said: "O Messenger of Allah (peace and blessings be upon him), what is lawful for us from these which you have ordered to be killed?" So Allah Almighty revealed this verse: "They ask you what is lawful for them. Say: Good and pure things have been made lawful for you, and the hunting dogs you have trained." [Surah al-Ma'idah: 4]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجزية / 18866