The Messenger of Allah ﷺ said, "My nation will split into two factions, and from between them a renegade group will break away. The faction closer to the truth will be the one to kill them."
حدثنا يحيى عن عوف حدثنا أبو نضرة
قال رسول الله ﷺ يفترق أمتي فرقتين فيتمرق بينهما مارقة يقتلها أولى الطائفتين بالحق
Its isnad is sahih. Awf is Ibn Abu Jameelah al-Arabi, who is trustworthy. The hadith is in Bukhari 12/282, no. 6931 (Fath), and Muslim 2/745, no. 1065, in the chapter on zakat, mention of the Kharijites, and all the compilers of the Sunan have it.His saying "fa-yatamarraq," and in another version "fa-tamarraq," means "it goes out from both groups," and there is no doubt that these are the Kharijites, who do not belong to anything reasonable that the intellect would accept. There is no doubt that they exist in every era, and their harm to Islam is greater than that of its enemies.