Musnad Ahmad #806

It was narrated that Tariq bin Ziyad said: We went out with ‘Ali to the Khawarij, and he fought them and killed them. Then he said: Look, for the Prophet (ﷺ) of Allah said: “There will emerge people who speak the truth but it will not go further than their throats; they will pass out of the truth as the arrow passes through the prey. Their sign is that among them will be a black man with a deformed hand, with black hairs on his hand.” If it is him, you will have killed the worst of people, and if it is not him, you will have killed the best of people.” We wept, then he said: Go and look. So we looked, and we found the one with the deformity. We fell down in prostration and ‘Ali fell down in prostration with us, but he said: `They speak the word of truth.”