Islamic mysticism had several stages of growth, including (1) the appearance of early asceticism, (2) the development of a classical mysticism of divine love, and (3) the rise and proliferation of fraternal orders of mystics. Despite these general stages, however, the history of Islamic mysticism is largely a history of individual mystic experience.
The first stage of Sufism appeared in pious circles as a reaction against the worldliness of the early Umayyad period (AD 661-749). From their practice of constantly meditating on the Qur'anic words about Doomsday, the ascetics became known as "those who always weep" and those who considered this world "a hut of sorrows." They were distinguished by their scrupulous fulfillment of the injunctions of the Qur'an and tradition, by many acts of piety, and especially by a predilection for night prayers.
The introduction of the element of love, which changed asceticism into mysticism, is ascribed to Rabi'ah al-'Adawiyah (died 801), a woman from Basra who first formulated the Sufi ideal of a love of God that was disinterested, without hope for paradise and without fear of hell. In the decades after Rabi'ah, mystical trends grew everywhere in the Islamic world, partly through an exchange of ideas with Christian hermits. A number of mystics in the early generations had concentrated their efforts upon tawakkul, absolute trust in God, which became a central concept of Sufism. An Iraqi school of mysticism became noted for its strict self-control and psychological insight. The Iraqi school was initiated by al-Muhasibi (died 857)--who believed that purging the soul in preparation for companionship with God was the only value of asceticism. Its teachings of classical sobriety and wisdom were perfected by Junayd of Baghdad (died 910), to whom all later chains of the transmission of doctrine and legitimacy go back. In an Egyptian school of Sufism, the Nubian Dhu an-Nun (died 859) reputedly introduced the technical term ma' rifah ("interior knowledge"), as contrasted to learnedness; in his hymnical prayers he joined all nature in the praise of God--an idea based on the Qur'an and later elaborated in Persian and Turkish poetry. In the Iranian school, Abu Yazid al-Bistami (died 874) is usually considered to have been representative of the important doctrine of annihilation of the self, fana' (see below); the strange symbolism of his sayings prefigures part of the terminology of later mystical poets. At the same time the concept of divine love became more central, especially among the Iraqi Sufis. Its main representatives are Nuri, who offered his life for his brethren, and Sumnun "the Lover."
The first of the theosophical speculations based on mystical insights about the nature of man and the essence of the Prophet were produced by such Sufis as Sahl at-Tustari (died c. 896). Some Hellenistic ideas were later adopted by al-Hakim at-Tirmidhi (died 898). Sahl was the master of al-Husayn ibn Mansur al-Hallaj, who has become famous for his phrase ana al-haqq, "I am the Creative Truth" (often rendered "I am God"), which was later interpreted in a pantheistic sense but is, in fact, only a condensation of his theory of huwa huwa ("He he"): God loved himself in his essence, and created Adam "in his image." Hallaj was executed in 922 in Baghdad as a result of his teachings; he is, for later mystics and poets, the "martyr of Love" par excellence, the enthusiast killed by the theologians. His few poems are of exquisite beauty; his prose, which contains an outspoken Muhammad-mysticism--i.e., mysticism centred on the prophet Muhammad--is as beautiful as it is difficult.
Sufi thought was in these early centuries transmitted in small circles. Some of the shaykhs, Sufi mystical leaders or guides of such circles, were also artisans. In the 10th century, it was deemed necessary to write handbooks about the tenets of Sufism in order to soothe the growing suspicions of the orthodox; the compendiums composed in Arabic by Abu Talib Makki, Sarraj, and Kalabadhi in the late 10th century, and by Qushayri and, in Persian, by Hujviri in the 11th century reveal how these authors tried to defend Sufism and to prove its orthodox character. It should be noted that the mystics belonged to all schools of Islamic law and theology of the times.
The last great figure in the line of classical Sufism is Abu Hamid al-Ghazali (died 1111), who wrote, among numerous other works, the Ihya' 'ulum ad-din ("The Revival of the Religious Sciences"), a comprehensive work that established moderate mysticism against the growing theosophical trends--which tended to equate God and the world--and thus shaped the thought of millions of Muslims. His younger brother, Ahmad al-Ghazali, wrote one of the subtlest treatises (Sawanih; "Occurrences" [i.e., stray thoughts]) on mystical love, a subject that then became the main subject of Persian poetry.