Mukhtasar Muslim

Sayyiduna Abu Dharr (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings be upon him) said: When any one of you stands for prayer and there is an object in front of him equal to the back part of a saddle, then that is sufficient as a barrier for him. If there is not an object of that size (or higher) in front of him, and a donkey, a woman, or a black dog passes in front of him, then his prayer is invalidated. I said: O Abu Dharr (may Allah be pleased with him)! What is special about a black dog, and not a red or yellow dog? He said: O my nephew! I also asked the Messenger of Allah (peace and blessings be upon him) just as you have asked me, and he (peace and blessings be upon him) said: The black dog is a devil.