The Kharijites were the first group to emerge with extremist views in the name of Islam. When the political disagreement between Ali ﵁ and Muawiyah ﵁ arose, the two leaders resolved the issue through arbitration. However, a group of individuals dissatisfied with this approach misinterpreted the Quranic verse, "Judgment belongs to Allah alone" (Quran), to justify their stance. They claimed that certain companions of the Prophet, had committed shirk (polytheism) by seeking human judgment.
This group believed that the Companions of the Prophet who sought human judgment, thereby usurping Allah's authority, had committed shirk (polytheism) and became disbelievers (kafirs). They held that it was obligatory to fight these disbelievers first.
Meanwhile, another group emerged, excessively glorifying Ali ﵀ and arguing that he was the rightful first caliph and that Abu Bakr ﵁ and others had wronged him. This group would later become known as the Shiites