It is narrated from Hazrat Abu Dharr (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: If a person does not have even the rear part of a saddle in front of him, then his prayer will be invalidated if a woman, a donkey, or a black dog passes in front of him. The narrator asked: What is the difference between a black dog and a red dog? Hazrat Abu Dharr (may Allah be pleased with him) replied: Nephew! I also asked the Noble Prophet (peace and blessings be upon him) the same question as you have asked me, so the Noble Prophet (peace and blessings be upon him) said: The black dog is a devil.