صحيح مسلم

Abu Sai'd al-Khudri reported: When we were in the company of the Messenger of Allah (ﷺ) and he was distributing the spoils of war, there came to him Dhul-Khuwasira, one of Banu Tamim. He said: Messenger of Allah, do justice. Upon this the Messenger of Allah (ﷺ) said: Woe be upon thee! Who would do justice, if I do not do justice? You would be unsuccessful and incurring a loss, if I do not do justice. Upon this Umar b. Khattab (Allah be pleased with him) said: Messenger of Allah, permit me to strike off his neck. The Messenger of Allah (ﷺ) said: Leave him, for he has friends (who would outwardly look to be so religious and pious) that everyone among you would consider his prayer insignificant as compared with their prayer, and his fast as compared with their fasts. They would recite the Qur'an but it would not go beyond their collar-bones. They would pass through (the teachings of Islam so hurriedly) just as the arrow passes through the prey. He would look at its Iron head, but would not find anything ticking) there. He would then see at the lowest end, but would not find anything sticking there. He would then see at its grip but would not find anything sticking to it. He would then see at its feathers and he would find nothing sticking to them (as the arrow would pass so quickly that nothing would stick to it) neither excrement nor blood. They would be recognised by the presence of a black man among them whose upper arms would be like a woman's breast, or like a piece of meat as it quivers, and they would come forth at the time when there is dissension among the people. Abu Sai'd said: I testify to the fact that I heard it from the Messenger of Allah (ﷺ), and I testify to the fact that 'Ali b. Abu Talib fought against them and I was with him. He gave orders about that man who was sought for, and when he was brought in, and when I looked at him, he was exactly as the Messenger of Allah (ﷺ) had described him.