Abdullah bin al-Samit (may Allah have mercy on him) relates: I heard Sayyiduna Abu Dharr (may Allah be pleased with him) say that the Messenger of Allah (peace and blessings be upon him) said: "When there is nothing in front of the person praying equal to the back of a saddle, then a woman, a donkey and a black dog break his prayer." I said: "O Abu Dharr, what is the reason for the black colour? Why is the prayer not broken by a red or white dog?" He said: "My nephew, I 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.'"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3483