Abu Dharr said (and not the Prophet): If there is not anything like the back of a saddle in front of a man who is praying, then a donkey, a black dog, and a woman cut off his prayer. I asked him: Why has the black dog been specified, distinguishing it from a red, a yellow and a white dog? He replied: My nephew, I also asked the Messenger of Allah ﷺ the same question as you asked me. He said: The black dog is a devil. (Using translation from Abū Dāʾūd 702)   

أَنَّهُ قَالَ يَقْطَعُ صَلَاةَ الرَّجُلِ إِذَا لَمْ يَكُنْ بَيْنَ يَدَيْهِ كَآخِرَةِ الرَّحْلِ الْحِمَارُ وَالْكَلْبُ الْأَسْوَدُ وَالْمَرْأَةُ قَالَ قُلْتُ فَمَا بَالُ الْأَسْوَدِ مِنَ الْأَحْمَرِ مِنَ الْأَصْفَرِ فَقَالَ سَأَلْتُ رَسُولَ اللَّهِ ﷺ كَمَا سَأَلْتَنِي فَقَالَ «الْأَسْوَدُ شَيْطَانٌ»