Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) says: We were with the Prophet (peace and blessings be upon him) while he (peace and blessings be upon him) was distributing something, when Dhu al-Khuwaysirah, a man from Banu Tamim, came and said: O Messenger of Allah, be just! He (peace and blessings be upon him) said: "Woe to you! Who will be just if I am not just? You would have failed and lost if I were not just." Sayyiduna Umar (may Allah be pleased with him) said: Permit me to strike his neck. He (peace and blessings be upon him) said: "Leave him, for he has companions alongside whose prayer and fasting you would consider your own prayer and fasting insignificant. They recite the Qur'an, but it does not go beyond their collarbones. They pass out of Islam as an arrow passes out of the game: its head is looked at and nothing is found on it, then its binding is looked at and nothing is found on it, then its shaft is looked at and nothing is found on it, then its feathers are looked at and nothing is found on them; it has outstripped the dung and the blood. Their sign is a black man, one of whose upper arms is like a woman's breast, or like a lump of flesh that quivers. They will emerge at a time when people are in division." Sayyiduna Abu Sa'id (may Allah be pleased with him) says: I bear witness that I heard this from the Prophet (peace and blessings be upon him), and I bear witness that Sayyiduna Ali (may Allah be pleased with him) fought them while I was with him; he ordered that man to be searched for, and he was brought, until I looked at him and found him matching the description the Prophet (peace and blessings be upon him) had given.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16702