Abu Dharr said that :
Allah's Messenger said: When a man performs Salat, and there is nothing in front of him like the post of a saddle, or a camel saddle, then his Salat is severed by (passing of) a black dog, a woman, and a donkey. It was said to Abu Dharr: What is the problem with the black dog rather than the red or white one? He said: O my nephew! I asked Allah's Messenger just as you have asked me. He said: 'The black dog is a Shaitan (devil).'