It wasnarrated that Abu Dharr said:
"I asked the Messenger of Allah(ﷺ)about the all-black dog and he said: '(It is) a devil.'" (RU)
English reference (RU): Vol. 4, Book 28, Hadith 3210 (RU)
Arabic reference (RU): Book 28, Hadith 3331 (RU)