Please note that when speaking about Sufism, we distinguish between the very early Sufism which consisted of somewhat of an exaggeration in worship and piety, entailing a departure from the moderate way of the Companions and between what came later of the esoteric, gnostic, illuminist, philosophical, heretical Sufism. Here Ibn Taymiyyah touches upon the origins of Sufism in Basrah.
Shaykh al-Islam Ibn Taymiyyah said:
The first [time] that the Sufiyyah appeared was from Basrah. The Imam Ma'mar bin Ziyaad, from the companions of al-Waahidee, mentioned in [his book] Akhbaar al-Sufiyyah, that the first convent (a type of monastery) built for them was in Basrah.
And the first of those who built the convent of the Sufis were the companions of Abd al-Wahid bin Zayd and Abd al-Wahid bin Zayd is from the associates of al-Hasan (al-Basree). In Basrah there was such exaggeration in zuhd (abstention), worship, fear and what is of its like that was not found in any of the other lands. For this reason, it used to be said, "Kufic jurisprudence and Basran worship."
For this reason, most of what is narrated of exaggeration in this subject is from the worshippers from the people of Basrah, such as the citation of the one who died or fainted upon hearing the Qur'an and what is like this. [Also] such as the story of Zaraarah bin Awfee, the qaadee (judge) of Basrah, he recited, "Yet when the Trumpet is sounded" (74:8), he fell down dead. And such as the story of Abu Juhayr al-A'maa to whom Saalih al-Murree recited and he died. And similarly, others about whom it has been reported that they died after listening to the reciting (of the Qur'an), and there used to be amongst them factions who would fall unconscious when hearing the Qur'an.
The intent here [is]: That these affairs in which there is an additional increase in worship and states of being (ahwaal), they appeared out of Basrah, and this was due to the severity of [reverential] fear (arising from them). For what they mention of the fear (khawf) of Utbah al-Ghulaam, Ataa al-Sulaymee [from the Taabi'een] and their likes is a great affair. And there is no doubt that their state is more perfect and superior than the one who does not have such awe of Allaah that equals theirs or is superior to theirs. Yet whoever feared Allaah with a moderate fear (khawf) that invites him to do what Allaah loves and abandon what Allaah dislikes, without this addition (of exaggaration in fear), then his state is more perfect and superior than the state of those (the Basran Sufis), and this is the state of the Companions (radiyallaahu anhum).
And it has been narrated that Ataa al-Sulaymee was seen after his death (in a dream), and it was said to him, "What has your Lord done with you?" And he said, "He (Allaah) said to me: Do you not feel shy of Me that you fear Me to this level?! Has it not reachedd you that I am forgiving (ghafoor), merciful (raheem)?!"
Refer to Majmu al-Fatawa (11/6-7).