The early history of Sufism is not yet clear. It seems to have emerged from a determination among some early Muslims not to be distracted by the rapid Muslim expansion over vast territories from the vision and practice of Muḥammad in realizing the absolute sovereignty of God in life. Of this early attitude, al-Ḥasan al-Baṣrī (Basra being an important centre of it) is a major example, and later Sūfī orders look back to him as a key link in the connection back to the Prophet. Also from Basra was the notable Rabiʿa al-ʿAdawiyya; but Sūfī devotion took root in many different places, often absorbing in each place something of its different atmosphere. Thus Khurasāni Sufism reflected its parched surroundings in an austere asceticism, producing such remembered figures as Fudayl ibn ʿIyad, Ḥātim al-Aṣamm (who left behind the four principles of Sūfī life, to remember that no one eats your daily bread for you, that no one performs your acts except yourself, that as death is hurrying toward you so address your life now to meet it, and that every moment of your life is under the eye and judgement of God), and Ibrāhīm ibn Adham. The latter was a prince who experienced a dramatic conversion when out hunting.
Or again Kashmiri Sufism, from the 14th cent. onward, drew on Hindu asceticism, even producing an order, the Rishis, whose name was derived from the word ṛṣi (understood as ‘a singer of sacred songs’).
Since Sufism was a commitment to God in absolute trust and obedience, it (unsurprisingly) gave rise to intense experience of that relationship. Techniques were developed (e.g. dhikr, samaʿ) which were capable of producing trance states of ecstasy. The realized condition of union with God produced such a sense of the absolute truth of God, and of the bliss of union with him, that poetry and teaching began to emerge in which the distinction between God and the self seemed to be blurred—or even obliterated: the disturbance this caused for those sensitive to the absolute transcendence of God can be seen in the fate of al-Ḥallāj, although far more threatening in effect was the mystically monistic system of ibn al-ʿArabī. Any potential conflict between the ʿulamā and the Sufis was largely overcome by the work of al-Ghaz(z)ālī, who knew both positions at first hand, and demonstrated the part that both play in Islam.
From the experience of devotion to God, the Sūfī poets, especially in Persia, produced works of enduring beauty and power. Among the earliest was Pīr-i-Anṣār (ʿAbdullah al-Anṣārī, d. 1088 (AH 481)), of Herat in Khurasān.
Other memorable poets were Farīd al-Dīn ʿAṭṭār, ibn al-Fāriḍ, Jāmī, and perhaps consummately Jalāl al-Dīn Rūmī.
The wide extent and influence of Sufism led to attempts being made to give systematic order to its teachings and techniques—a notable example being Ali Hujwīrī (d. 1702). But even more important was the organization of Sūfī traditions into formal orders (tarīqa, pl. turūq; silsilah). For examples, see CHISHTI; MAWLAWIY(Y)A; NAQSHBANDIY(Y)A; QĀDIRIY(Y)A; SHĀDHILIY(Y)A. An adherent is known (in general terms, though these words also have a wider use) as derwīsh, faqīr, marabout.
A leader is known as shaykh.
"Sūfīs." The Concise Oxford Dictionary of World Religions. . Encyclopedia.com. (February 16, 2019). https://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/sufis
"Sūfīs." The Concise Oxford Dictionary of World Religions. . Retrieved February 16, 2019 from Encyclopedia.com: https://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/sufis