(47) باب ذِكْرِ الْخَوَارِجِ وَصِفَاتِهِمْ
Abu Sa'id al-Khudri reported that the Messenger of Allah (ﷺ) said:
A group would secede itself (from the Ummah) when there would be dissension among the Muslims. Out of the two groups who would be nearer the truth would kill them.
Reference: Sahih Muslim 1065 b
In-book reference: Book 12, Hadith 195
USC-MSA web (English) reference(deprecated numbering scheme): Book 5, Hadith 2325