Ultimately, the Holy Koran Is the Only Source of Authority in Islam

The Holy Qur'an, most sacred book of Islam, is a collection of revelations from Allah to the Prophet Muhammad. The Qur'an acts as a guide for the Muslim, covering all aspects of everyday Muslim life. The Qur'an is by far the most important and influential foundation of Islam, but it is not the only source of authority. In addition to the Qur'an, the Sunnah of the Prophet, preserved in the hadiths, offers guidance on proper Islamic conduct. The approved practice of the community (ijma) is another source of authority, while Ijtihad is the practice of finding judgement on issues not covered in the Qur'an. Additionally the Sharia is the body of laws which govern the Islamic state. While there are several sources of authority in Islam, the Qur'an is overwhelmingly the most important, and it is only through the Qur'an that other sources gain their stature.
It cannot be doubted that the Qur'an is the 'supreme authority' of Islam.
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