al-Muhasibi

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.

The Sufis of his time had taken on certain practices, such as wearing woolen clothing, reciting the Qur'an at night, and limited the kind and quantity of food eaten.

Constant self-examination in anticipation of the Day of Judgement was his proposed method for developing an awareness of the inner self and purifying the heart.

Al-Muhasibi later joined a group of scholars of theology, led by Abdullah ibn Kullāb (died 855) and al-Karibisi.

In 848 (or possibly 851), the caliph al-Mutawakkil ended the Mihna (a period of religious and ideological persecution) and two years later, banned the Mu'tazilites' theology.