Though there is no single founder or group of foundational figures, in the first centuries of Islam and especially in the great cities of the east, such as Baghdad and Basra, certain men and women had a tremendous impact on their own circles of disciples and students, who would go on to shape the mystical tradition.One of the most essential yet least understood early figures in the Sufi tradition, al-Hasan al-Basri (d. 728 C.E), lived in Basra, modern day Iraq. He and his students are among the earliest proponents of asceticism (zuhd, in Arabic), and their legacy influenced the early development of the Sufi movement. Unfortunately, Al-Hasan al-Basri's life is shrouded in some degree of mystery, and the historicity of many accounts about his life and practice is questionable. He nonetheless remained an important figure for later Sufis, who may have been appropriating his myth without much care for its historical veracity.
Born in Medina, in Arabia, to Persian parents who may have been slaves, Al-Hasan al-Basri is said to have grown up in the company of Muhammad's Companions, and is said by some sources to have been raised by one of Muhammad's wives, Umm Salama, though this is doubtful. It is more likely that this story was invented by later Sufis who, in support of Al-Hasan al-Basri, wanted to establish his legitimacy by linking him to important historical persons. He lived during a time of turbulence in the Islamic world, and was witness to rebellions against the Umayyad regime led by Ibn al-Zubayr and Ibn al-Ash'ath. Eager to keep his reputation from being blemished, Al-Hasan al-Basri's followers circulated various reports claiming that he refused to take sides in the rebellions.
In addition to political turmoil, Al-Hasan al-Basri's name and reputation were entangled in the greatest theological dispute of his day. According to some, he held to a doctrine of free will, or "Qadarism," against the doctrine of predestination. Confusingly, he is also reported to have held the opposite view, against the proponents of free will. It may be impossible to determine what his actual, as opposed to his represented, views were, but it seems clear that he was a proponent of early Muslim asceticism, a fact for which he is highly respected by Sufis.
Part of the confusion stems from a general murkiness in medieval Islamic sources around the word "Qadarism," which at times can mean "proponent of free will" and at other times can mean the exact opposite, a belief in "predetermination." Other movements that were explicitly predestinarian arose in opposition to proponents of free will, and neither side of this question would be more likely to lean toward Sufism than any other. It is a merely a testament to Al-Hasan al-Basri's reputation that all sides, Sufi or not, claim him as their intellectual forefather.
More than a century after Al-Hasan's death, in Baghdad, a man named Al-Junayd ibn Muhammad (d. 910 C.E.) became a leader of a Sufi school, and quickly became an authority for later tradition. His teachings about the annihilation of the self and cultivation of inner spiritual discipline were a less ambiguous endorsement for the Sufi way of life than was Al-Hasan al-Basri's. He is also credited with having pioneered a brand of Sufism known as "sober Sufism," which sought to transcend the competing trend of ecstatic, or "intoxicated" mystical practice. (Intoxication here refers to an ecstatic state into which some Sufis would enter, and which could be brought on by group invocations, rhythmic breathing, music, or dance, depending on the branch of Sufism involved.)
Al-Junayd's practical approach to worldly matters is attested to by his declaration at the trial of fellow mystic Al-Hallaj, who had been charged with blasphemy for his more extreme views regarding his own union with God, which he claimed to have achieved during an ecstatic episode. Al-Junayd, unwilling to comment on Al-Hallaj's inner disposition, pronounced his opinion that judging such matters should rely only on an assessment of outward appearances.
Sufi circles, like schools of historical tradition or legal thought, were to some extent defined even further by geography. There is no set of founding fathers or delineated schools of thought in the Sufi tradition, but there are some influential foundational figures: