Not everything that goes under the name of Sufism is considered Islamic, just as not everything that goes under the name of Fiqh (jurisprudence) can be considered as authentic or proper Fiqh.

 In order to judge something as Islamic, it must be judged and weighed by the well-established criteria and standards of Shari`ah as enshrined in the Book and the Sunnah.

Thus if a certain Sufi practice or custom is opposed to the prescribed criteria of the Shari`ah as enshrined in the Qur’an and the Sunnah, it shall be judged as un-Islamic; if, however, it agrees with these criteria it shall be judged as perfectly Islamic.

Outstanding Muslim scholars have divided Sufism into two broad categories in order to determine its compatibility or non-compatibility with the Shari`ah. 

Firstly, genuine and authentic Sufism, which is undoubtedly in perfect agreement with the Book, theSunnah, and the practices of Salaf As-Salih (early righteous Muslims). Tasawwuf of Sufi masters such as Junyad Al-Baghdadi, Abu Sulayman Al-Darani, etc. belong to this category of authentic and genuine Tasawwuf. 

Secondly, pseudo-Sufism which includes those who uphold and advocate cultic practices or customs that are contrary to the Sunnah, as well as those who have mixed Sufism with speculative Mysticism/Neo-Platonism, and thus dabble in metaphysical theories about cosmos, emanations, etc. Both these groups are charlatans and impostors. While the former invent new forms of `Ibadah(acts of worship) that are not sanctioned by the Law-giver, the latter mix philosophy with religion and blur the essential distinction between the Creator and creation, which is the basis of Prophetic religion. There is no doubt that indulgence in such forms of Sufism takes humans away from their true purpose and mission in life which is to do God’s will on earth. These pseudo-Sufis turn the goal of human life into contemplation of mysteries of the universe; it is contrary to the Qur’anic definition of the purpose of human existence.

It is because of the real dangers inherent in such aberrations, and deviations that the early Sufi masters tirelessly preached the importance of weighing everything by the firm yardstick of theShari`ah: Abu Al-Qasim Al-Junayd, one of the genuine masters of authentic Tasawwuf, said, "The essence of Tawhid(monotheism) is to distinguish the eternal from the temporal”; he also said, “Whoever does not retain the Qur’an, nor studies the Hadith cannot be trusted in this matter (Tasawwuf) since our knowledge is bound solely by the teachings of the Book and the Sunnah."

Abu Sulayman Ad-Darani said, “Often one of the insights of the Sufi folk occurs to me and yet I do not accept it until I examine it by the testimony of the two of the most reliable witnesses: the Book of Allah and the Sunnah of the Prophet, peace and blessings be upon him.

According to an eminent scholar, “Authentic Tasawwuf is at once a cognitive and practical discipline of souls, curing of diseases of hearts, implanting of virtues, and purging souls off their vices and carnal desires, and training in patience, contentment and obedience to Allah; it is struggle against the carnal soul, and combating its base inclinations and meticulous scrutiny of actions and non-actions, and guarding souls against the invasions and influx of heedlessness and vain thoughts, and severing off all hindrances and obstacles that hinder and hamper one’s journey to Allah; it is asceticism in everything that distracts a person from celebrating remembrance of Allah and make one’s hearts focused on it. It is knowledge of Allah and conviction in Him, affirming His Oneness and glorifying Him, and turning wholly unto Him, and turning away from everything else; it is to be solely focused entirely on worshipping and obeying Allah, and compliance with His limits, and acting according to His Shari`ah, and exposing oneself to the graces and gifts that Allah vouchsafes to His chosen servants as a sheer sign of His grace and mercy.”

Another scholar said, “Tasawwuf is to adorn oneself with every noble traits of character and to shun every base one.” Or, stated differently, “It is to examine one’s states and cling to noble manners.”

When defined in this way Tasawwuf is not only an authentic Islamic discipline but the quintessence of Islam as an experiential reality.” 

http://www.onislam.net/english/ask-the-scholar/ideologies-movements-and-religions/175638-is-sufism-islamic.html?Religions=

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