Sufism, Muslim mysticism, is a phenomenon inherent in Islam, existing almost from the beginning of this religion. In the article the view of Islamic sacred texts: the Qur’an and the Hadith, to the basic principles of Sufi sm: asceticism and meditation is discussed. The most important concepts of Sufi sm arising during the period of singular mystics, i.e. the formative times of Sufi sm (9th-11th century) are underlined. Concepts such as love for God, self-accountability, piety, and Union with God were presented and interpreted. Attention was also paid to the biographies of the most important mystics from this period, as recorded in the works of their successors.