Who is Al-Harith Al-Muhasibi, and what is the ruling on reading his books? Are they beneficial?

Al-Harith al-Muhasibi, whose full name was Abu Abdullah al-Harith ibn Asad al-Baghdadi, was an ascetic and pious scholar who authored numerous works on asceticism, spiritual refinement (al-raqa'iq), and refutations of opponents. His books were criticized and abandoned for two reasons: 1. His falling into the innovations of the Kullabiyyah (predecessors of the Ash'ariyah) by denying some of Allah's attributive qualities (sifat khabariyyah) and voluntary actions, which contradicts the methodology of the righteous predecessors (Salaf Saliḥ). 2. His excessive scrutiny in the matter of passing thoughts (khatarat) and whispers (wasawis), which goes against the leniency and ease of Islamic law (Shari'ah).

Imam Ahmad ibn Hanbal and Abu Zur'ah al-Razi testified to his innovativeness (bid'iyyah) and forbade sitting with his books, warning against them and their methodology. Al-Dhahabi mentioned that al-Muhasibi delved into a small amount of theological discourse (kalam), for which he was resented.

However, Shaykh al-Islam Ibn Taymiyyah denied that Ahmad's abandonment of al-Muhasibi was for the reason mentioned by al-Ghazali. Rather, it was because he held the view of Ibn Kullab on some issues concerning attributes. Ibn Taymiyyah indicated that al-Muhasibi repented from that, and that al-Harith himself encouraged adherence to the path of the Prophet's companions (peace be upon him) and warned against innovations.

In summary: What was held against al-Muhasibi did not exclude him from the fold of Ahl al-Sunnah, and he retracted some of what was criticized concerning him. A student of knowledge can benefit from his books while being cautious of the aforementioned criticisms.