Musnad Ahmad 834:27

Muhammad ibn Ja'far and Bahz narrated to us, they said: Shu'bah narrated to us, from Abu al-Tayyah, he said: I heard Mutarrif narrating from Abdullah ibn Mughaffal, he said: The Messenger of Allah, peace and blessings of Allah be upon him, commanded the killing of dogs. Then he said: "What is the matter with you and the dogs?" Then he granted a concession for the hunting dog and the sheep dog. And he said regarding the vessel: "If a dog laps from it, wash it seven times, and rub it with earth on the eighth."