ʿAbd Allāh b. Ḥafīf, one of the most renowned Sufis (mutasawwif) raised in Shiraz, was a Sufi who, on the one hand, acted with caution regarding "shathiyāt" (ecstatic utterances), while on the other hand, displayed such openness that he visited Hallāj in prison and described him as an "ʿālim-i rabbānī" (divinely inspired scholar).
The most valuable source concerning his life and ideas is the Sīra, written in Arabic by his murīd (disciple) Daylamī. The work would later be translated into Persian by Rukn al-Dīn Yaḥyā.
Another channel of influence for Ibn Ḥafīf, who was known as Shaykh al-Kabīr (the Great Shaykh), is the Kazerūniyya tariqa (a Sufi path/order), which was influential in the Islamic world for many years.
The statement, often said about many Sufis, that "Jews, Christians, and Magians were present at his funeral prayer and offered dua (supplication)," is also narrated regarding Ibn Ḥafīf.
A few more Sufis (mutasawwif) who lived in the 9th century and contributed to the recognition, spread, establishment, and endearment of this thought through their ideas, works, and disciples can be listed: Dhū al-Nūn al-Miṣrī, Fuḍayl b. ʿIyāḍ, Maʿrūf Karkhī, Sarī al-Saqaṭī, Bishr al-Ḥāfī, Shaqīq al-Balkhī, Sahl al-Tustarī, Abū Sulaymān al-Dārānī, Yaḥyā b. Muʿādh, Aḥmad b. Ḥadrawayh, Abū Turāb al-Nakhshabī...