(12) The Book of Zakat
كتاب الزكاة
(49) Chapter: The Khawarij are the most evil of people and of all creation
(49) باب الْخَوَارِجُ شَرُّ الْخَلْقِ وَالْخَلِيقَةِ ‏
Sahih Muslim 1068 b 

This hadith had been transmitted by Sulaiman Shaibani with the same chain of narrators (and the words are)," There would arise out of (this group) many a group"

وَحَدَّثَنَاهُ أَبُو كَامِلٍ، حَدَّثَنَا عَبْدُ الْوَاحِدِ، حَدَّثَنَا سُلَيْمَانُ الشَّيْبَانِيُّ، بِهَذَا الإِسْنَادِ وَقَالَ يَخْرُجُ مِنْهُ أَقْوَامٌ ‏.‏
Reference : Sahih Muslim 1068b
In-book reference : Book 12, Hadith 208
USC-MSA web (English) reference : Book 5, Hadith 2337
  (deprecated numbering scheme)