There are three distinct but overlapping periods in Sufi history generally recognized by historians: classical, medieval, and modern. Sufism can be traced back to a pious minority within the early Islamic fold who felt that the more austere aspects of the Prophets teaching were being lost sight of in the midst of political expansion.
Within Islam's first century the Muslim leaders found themselves in possession of a vast empire, and, living off tribute money from the conquered, they "surrounded themselves with captive concubines and slaves, and lived on a scale of luxury unknown to their ancestors."2 The movement of protest against this worldliness ultimately resulted in both the legalistic and mystical schools of Islam.
For early Islamic ascetics fear of eternal punishment in hell was the primary incentive to piety. Eventually however, a fervent love for God, displayed by such early Islamic saints as the woman Rabbi'a al-Adawiya (d. 801) became a central theme, and provided a basis for emerging Sufi mysticism. Professor E.G. Browne notes that early Sufism was characterized by
... ascetism, quietism, intimate and personal love of God, and disparagement of mere lip service or formal worship. This ascetic Sufism...if influenced at all from without, was influenced rather by Christian monasticism than by Persian, Greek or Indian ideas.3
Over two centuries after the time of Muhammad, gnostic influences began to appear in some expressions of Islamic spirituality. Junayd of Baghdad, (d. 910), a transplanted Persian, was especially instrumental in the shaping of Sufism into a pantheistic system. He wrote: "Whatever attains to True Being is absorbed into God and becomes God."4 Another Persian, al-Hallaj (d. 922), executed for blasphemy, became celebrated as a martyr among medieval Sufis, particularly Persian poets. Hallaj, who traveled extensively and developed quite a following, scandalized the orthodox with statements like "I am the Truth."
Quietism, with its emphasis that God is all that matters and man is merely an instrument in His hands, provided fertile ground for the pantheistic beliefs that God is all there is, and man and the phenomenal world are merely shadows or emanations of His being.