Quranists believe Muhammad himself was a Quranist and the founder of Quranism, and that his followers distorted the faith and split into schisms and factions such as Sunni, Shia, and Khawarij. Quranists reject the hadith and follow the Quran only. The extent to which Quranists reject the authenticity of the Sunnah varies, but the more established groups have thoroughly criticised the authenticity of the hadith and refused it for many reasons, the most prevalent being the Quranist claim that hadith is not mentioned in the Quran as a source of Islamic theology and practice, was not recorded in written form until more than two centuries after the death of the Muhammed, and contain perceived internal errors and contradictions.