Imam Al-Hārith ibn Asad Al-Muhāsibī was born in the city of Basrah and lived and died in the city of Baghdad in the year 243 after the Hijrah. He was one of the Pious Predecessors (Salaf) of this Ummah and a contemporary of Imam Ahmad ibn Hanbal. He was called ‘Al-Muhāsibī’ due to his constant reckoning of himself, taken from the word ‘Muhāsib’ that means ‘One who takes account of something.’
Imam Al-Muhāsibī was most famous for his purity of faith and righteousness. And he is an example of a true Sūfī as understood in its true and original meaning, not as understood by many today as being one who worships dead people, or whirls in circles for hours on.
He was a scholar in all of the traditional Islamic Sciences: Aqīdah, Fiqh, and Tasawwuf (i.e. Iman, Islam, and Ihsān), and he excelled at each one of them. He is believed to have met and studied with Imam Shāfi’ī and followed his madhhab (School of Law).
Imam Al-Muhāsibī – despite enjoying such prestige – wasn’t free of opposition from certain scholars of his time due to the fact that he took an approach that was different from many of the scholars of his age.
The second and third centuries of Islamic History was the era of hadīth documentation and the development of the hadīth sciences. So most of the major scholars of the time were focused on the preservation of hadīth and distinguishing fabricated and weak reports from those that were sound.
Imam Al-Muhāsibī on the other hand, was inspired to focus on the purification of the heart and understanding the human psyche. So he would question his students about their thoughts and inclinations, try to understand them and how to cure those that were mischievous, and then he would write books inspired only by spiritual intuitiveness as opposed to what came in the form of scripture.
For this reason, some of the scholars of his time severely criticized him, and cautioned people against reading his books. For instance, when Abu Zur’ah Al-Rāzī was asked about him and his books, he said:
“Beware of these books…Innovations and deviances. Be obliged by what is transmitted. For verily, you’ll find in it what will avail you from these books.” It was then said to him, “But there is useful consideration (‘ibrah) in these books.” He replied, “Whoever doesn’t have useful consideration in the Book of Allah, then he has no useful consideration in these (books). Has it reached you that Mālik, Thaurī, Auzā’ī, or any of the Imams wrote books about insidious notions (khatarāt) and mischievous whisperings (wasāwis) and these things? These are people who have gone against the People of Knowledge. They come to us sometimes with Al-Muhāsibī, other times with ‘Abdur-Rahīm Ad-Dayabalī, and other times with Hātim Al-Asamm.” Then he said, “How quick are people to innovations!”
Anyone who is acquainted with the writings of Imam Al-Muhāsibī will quickly realize that these comments made by Imam Abu Zur’ah are unjustified and clearly shows the intolerance of those traditionally termed as Ahlul-Hadīth for anyone who took an approach different from theirs.
If there is any bid’ah (innovation) that Al-Muhāsibī is guilty of it is merely that he didn’t take the same approach as that of those like Abu Zur’ah, while it escaped the Imam (Abu Zur’ah) that his approach was also a bid’ah, since it was something that neither the Prophet nor his companions embarked upon. So not every bid’ah is blameworthy.
As for Imam Ahmad’s contention with Al-Muhāsibī, it isn’t totally clear except that scholars have given a few different reasons. Some say that Imam Ahmad criticized Al-Muhāsibī because of the books that he wrote in refutation of some deviant sects of Islam like the deniers of the divine decree (Qadarīyah). The problem was that in his books he would thoroughly explain or at least mention some of the arguments posed by the deviant groups. So he forbade people to read Al-Muhasibī’s, so they wouldn’t be exposed to the deviant doctrines.
Some say that Imam Ahmad took issue with Al-Muhāsibī’s statement that Allah speaks without words or sound. Ahmad’s view was that such additions shouldn’t be made. Rather, one should limit one’s self to saying that Allah speaks and has the attribute of speech, since the Salaf didn’t go into detail about such matters. Al-Muhāsibī’s position on the other hand was the natural result of his debates with deviant sects who equated Allah’s speech to the speech of his creatures by saying that it is with letters and sound. And Allah says, ((There is nothing like unto Him)). So in defense of orthodox doctrine he indulged in such matters. So it was merely a difference in approach that resulted from the urgency of the situation.
Another version has it that Imam Ahmad merely forbade people from reading Al-Muhāsibī’s books, because he knew that most people could not walk the steep path that he was on as Imam Al-Khatīb Al-Baghdādī reported with a sound chain that Imam Ahmad heard the words of Al-Muhāsibī during a lecture he gave to some of his students, and Ahmad said to one of his companions,
“I’ve never heard about the realities (of things) the like of this man. My opinion is that you shouldn’t accompany them.”
Ibn Hajar says,
“He only forbade him from accompanying them due to his knowledge that he was below their state. For verily, he was in a straitened state that every one cannot pursue. And it is feared that the one who pursues it will not give it its due.”
But whatever the reason Imam Ahmad may have objected to the writings and approach of Al-Muhāsibī, from one Salaf to another, each was entitled to his own opinion, especially since the days of revelation had already passed. Only Allah can settle the dispute between the two of them.
For this reason, Imam Tāj al-Dīn Ibn Al-Subkī says after commenting on what happened between these two great scholars,
“It is proper for you – O ye seeking direction – to travel the path of discipline with the past Imams, and not look at the comments of some of them about others unless he brings clear proof. Then if you are able to give an interpretation and entertain a good opinion, then obligingly do so! Otherwise, ignore what happened between them. For verily, you haven’t been created for this. So be preoccupied with what concerns you, and leave off what does not concern you. And the seeker of knowledge remains noble in my eye until he indulges in what has happened between the Past Predecessors, and he judges in favor of some of them over others.
So beware! Then beware to turn your attention to what unexpectedly happened between Abu Hanīfah and Sufyān Al-Thaurī, between Mālik and Ibn Abī Dhi’b, between Ahmad ibn Sālih and Al-Nasā’ī, between Ahmad ibn Hanbal and Al-Hārith Al-Muhāsibī, etc. until the time of ‘Izz al-Dīn ibn ‘Abd al-Salām and Sheikh Taqī al-Dīn Ibn Al-Salāh! For if you become preoccupied with that, I fear your destruction. The men are distinguished Imams. And there are ways of construing their words. Perhaps, some of them weren’t understood. So we have no right but to be pleased with them and to keep silent about them as is done regarding what happened between the Companions (Sahābah) – may Allah be pleased with them.” 
 He is Mālik ibn Anas ibn Mālik Abū ‘Āmir ibn ‘Amr Al-Aşbahī Abū ‘Abdillah, the Medinite Jurisprudent, and the Imam of Dār Al-Hijrah, The chief of the specialists. Imām Bukhārī said: “The soundest of all chains is: Mālik from Nāfi’ from Ibn ‘Umar.” He died in the year 179 a.h. And he was born in the year 93 a.h. Al-Wāqidī said: “He attained 90 years.” [Taqrīb al-Tahdhīb: (2/6685)]
 He is Sufyān ibn Sa’īd ibn Masrūq Al-Thaurī, one of the distinguished Imams in Islamic history. He died in the year 261 a.h. [Taqrīb al-Tahdhīb: 1/216]
 His name is ‘Abd al-Rahmān ibn ‘Amr ibn Abī ‘Amr, the jurist and Imam who died in the year 257.
 Abū Zur’ah is ‘Ubaidullah ibn ‘Abd al-Karīm ibn Yazīd ibn Farrūkh Al-Makhzūmī, one of the great Imams and a prolific hadīth retainer (hāfiz). He died in the year 264 a.h. [Tahdhīb Al-Tahdhīb: 5/394]
 Tahdhīb al-Tahdhīb: 6/107.
 Tabaqāt al-Shāfi’īyah: 2/39.
The account given by Attar of al-Mohasebi, one of the greatest figures in the history of Islamic mysticism is surprisingly jejune. Born in Basra in 165 (781), Abu Abd Allah al-Hareth ibn Asad al- Basri al-Mohasebi early in his life removed to Baghdad where he studied Traditions and theology and was closely involved with the leading personalities and prominent events of his times. He died in 243(857).
The influence of his teachings and writings upon later mystical theorists, including in particular Abu Hamed al-Ghazali, was profound and far-reaching. Many of his books and pamphlets have been preserved, the most important being the Ketab al-Reaya (edited by Dr.
Margaret Smith, London, 1940).
The austerity of Hareth-e Mohasebi
Hareth-e Mohasebi inherited thirty thousand dinars from his father. Take it to the Treasury. Let the authorities have it, he ordered.
Why? they asked.
The Prophet said, he explained, and it is a true Tradition that the Qadarites are the Magians of this
community. My father was a Qadarite. The Prophet also said that a Muslim cannot inherit from a Magian.
My father was a Magian, as you see, and I am a Muslim.
Gods providence in preserving him was such that, when he stretched out his hand towards food whose
lawfulness was doubtful, a nerve in the back of his finger became taut so that the finger did not obey the
command to move. Thus he knew that the morsel in question was not proper.
Hareth came to me one day and was visibly hungry, reported Jonaid. Uncle, I will bring some food,
I said. That would be welcome, he answered. So I went to the larder and looked for some food. I found
some remains of a wedding-feast which had been brought to us for supper. I brought this a offered it to
him. His finger would not obey him. He put morsel in his mouth, but despite all his efforts it would not
down. He turned it about in his mouth, then at last he got and put it out in the porch and took his departure.
Later I questioned him about what had happened. Hareth said, I was certainly hungry, and I wanted to
please you. But God has given me a special sign, that any food that is doubtful will not go down my throat
and my finger refuses to touch it. For all that I tried, it would not go down. Where did that. food come from?
From the house of a kinsman of mine, replied.
Then I said, Today will you come to my house? I will, he replied. So we entered, and fetched a piece of
dry bread, and we ate. Hareth remarked, This is the kind of thing to offer dervishes.