Musnad Ahmad 31:779

Abu Ahmad narrated to us, Sufyan narrated to us, from Habib ibn Abi Thabit, from al-Dahhak al-Mashriqi, from Abu Sa’id al-Khudri, from the Prophet, peace and blessings of Allah be upon him, in a hadith he mentioned: "A group will emerge during a time of division among the people, and they will be killed by the party that is closer to the truth."