Sufism or taṣawwuf (Arabic: تصوّف) is defined by its adherents as the inner, mystical dimension of Islam. A practitioner of this tradition is generally known as a ṣūfī (صُوفِيّ). Sufis believe they are practicing Ihsan (perfection of worship) as revealed by Gabriel to Muhammad, "Worship and serve Allah as you are seeing Him and while you see Him not yet truly He sees you."
Classical Sufi scholars have defined Sufism as "a science whose objective is the reparation of the heart and turning it away from all else but God". Alternatively, in the words of the Darqawi Sufi teacher Ahmad ibn Ajiba, "a science through which one can know how to travel into the presence of the Divine, purify one's inner self from filth, and beautify it with a variety of praiseworthy traits".
Classical Sufis were characterised by their attachment to dhikr (a practice of repeating the names of God) and asceticism. Sufism gained adherents among a number of Muslims as a reaction against the worldliness of the early Umayyad Caliphate (661-750 CE). Sufis have spanned several continents and cultures over a millennium, at first expressed through Arabic, then through Persian, Turkish and a dozen other languages. "Orders" (ṭuruq), which are either Sunnī or Shī'ī or mixed in doctrine, trace many of their original precepts from the Islamic Prophet Muhammad through his cousin and son-in-law 'Alī, with the notable exception of the Naqshbandi who trace their origins through the first Caliph, Abu Bakr. Other exclusive schools of Sufism describe themselves as distinctly Sufi. Modern Sufis often perform dhikr after the conclusion of prayers.
Some mainstream scholars of Islam define sufism as simply the name for the inner or esoteric dimension of Islam. René Guénon in Insights into Islamic Esoterism and Taoism (Sophia Perennis 2003) contended that Sufism was the esoteric aspect of Islam supported and complemented by exoteric practices and Islamic law. However, according to Idries Shah, the Sufi philosophy is universal in nature, its roots predating the rise of Islam and the other modern-day religions, save for perhaps Buddhism and Jainism; likewise, some Muslims consider Sufism outside the sphere of Islam.