al-Muhasibi
Al-Muḥāsibī (Arabic: المحاسبي) (781–857 CE) was a Muslim Arab, theologian, philosopher and ascetic. He is considered to be the founder of the Baghdad School of Islamic philosophy which combined Kalam and Sufism, and a teacher of the Sufi masters Junayd al-Baghdadi and Sirri Saqti.
His full name is Abu Abdullah Harith bin Asad bin Abdullah al-Anizi al-Basri, and he hailed from the Arab Anazzah tribe. He was born in Basra in about 781. Muhasibi means self-inspection or audit. He was a founder of what later became the mainstream Sufi doctrine, and influenced many subsequent theologians, such as al-Ghazali.
The author of approximately 200 works, he wrote about theology and Tasawwuf (Sufism), among them Kitab al-Khalwa and Kitab al-Riaya li-huquq Allah (“Obeying God’s Permits”).