The religion of Islam, founded by Muhammad (also spelled Mohamed: the Glorified) in the 7th century AD, is based on the Quran, which is considered by Muslims as the word of God transmitted through the Archangel Gabriel to the Prophet Muhammad, the last in the series of biblical prophets. This religion contains an exterior or orthodox path and an interior or mystical path. The exterior path is based on the Law revealed in the Quran and primarily focuses on the observance of rules, rituals, and devotional acts. On the other hand, the interior or mystical path, called Sufism, deals with doctrine and the mystical path.
Source: Shiva Shambho
Documents on the Interior or Mystical Path
Books on the Interior or Mystical Path