Musnad Ahmad 937:141

Muhammad ibn Ja'far and Hajjaj narrated to us, they said: Shu'bah narrated to us, from Humayd ibn Hilal, from Abdullah ibn al-Samit, from Abu Dharr, from the Prophet, peace and blessings of Allah be upon him, that he said: "The prayer is interrupted if there is not in front of a man something like the back of a saddle: a woman, a donkey, and a black dog." I said: "What is the matter with the black [dog] as opposed to the red [one]?" He said: "I asked the Messenger of Allah, peace and blessings of Allah be upon him, just as you asked me, and he said: 'The black one is a devil.'"