Musnad Ahmad 31:34

Ibn Abi ‘Adi narrated to us, from Sulayman, from Abu Nadrah, from Abu Sa’id, that the Prophet, peace and blessings of Allah be upon him, mentioned a people who would be in his nation, emerging during a division among the people. Their mark is shaving [the head]. They are the worst of creation—or among the worst of creation. The closer of the two factions to the truth will kill them. He said: The Prophet, peace and blessings of Allah be upon him, struck a parable for them, or said a statement: "A man shoots an arrow—or he said: at the target—then he looks at the arrowhead and sees nothing, and he looks at the shaft and sees nothing, and he looks at the notch and sees nothing." Abu Sa’id said: And you killed them, O people of Iraq.