Thank you for the question.
Tasawuf (sufism) is a subject of the greatest dispute and debate among Muslims. Many Muslim scholars went to the extreme in denouncing it to the extent that they considered it as bid’ah (unauthentic acts of worship, which were not in Qur’an or sunna(example of the Prophet(pbuh)). To these scholars, tasawuf has no root in the Nobel Qur’an or in the traditions of the Prophet (pbuh). On the other hand, a large number of renowned scholars defended tasawuf and considered it as one of the important disciplines of Islamic teachings. One can find countless opinions, which consider sufis as kafirs (non-believers) or mubtade’een (those who apply bid’ah) and not part of the Muslim ummah (nation). On the other end, one can also find countless opinions stating that tasawuf is the right path for self- purification (tazkiya).
I personally adhere to the opinion of Ibn Taymiyah on this matter, which states: “A great dispute occurred regarding sufism. A group of Muslims extremely denounced sufis and sufism and said sufis are mubtade’een and are out of the sunna (the traditions) of the Prophet (pbuh). This opinion was adopted by a large number of imams (Islamic scholars) and transmitted later by people of fiqh (law) and people of ‘ilmu al-kalam (theology). Another group went too far in defending sufis and sufism. They claimed that sufis are the best among people and the most complete after prophets and messengers.
Both extreme opinions should not be acceptable. The right opinion should be that sufis are Muslims whom are striving hard to obey Allah (swt) like other Muslims who strive to obey Allah (swt) as well. Among the sufis there are those who are foremost in their good deeds, through their striving, and are near Allah and those who follow a middle course of striving. Also, among the two kinds of sufis there are those who do right and those who do wrong, and among them those who commit sin and repent, and those who commit sin and do not repent.
And it happened that some people claimed affiliation with sufism who were innovators and deviant Muslims. These people, al-Hallaj for instance, are rejected and denounced by the renowned scholars of sufism such as Al-Junaid Ibn Muhammad, the master of the sufis, and others.” (Refer to Majmu’atu al-Fatawa of Ibn Taymiyah, Vol. 11)
This was the opinion of Shaikh al-Islam Ibn Taymiyah about sufism, which I believe is the most reasonable and logical opinion about this subject matter. Moreover, all scholars, sufis and non-sufis, agreed that any religious practice that contradicts or has no root in the Qur’an and the traditions of the Prophet (pbuh) is not acceptable, according to Islam. Also, they agreed that the only sufism, which is acceptable is the one that is guided and fits within the right ‘aqidah (creed) of Islam. Sufism in this sense means a hard striving in purifying the soul and a hard striving to win the blessing of Allah (swt).
Among many scholars, including sufi scholars, the only acceptable sufism is the one that is continuously guided by the right ‘aqidah (creed), aims to purify one’s soul (tazkiyah), and adheres to the teachings of the shari’a (Islamic law). This type of sufism is not only acceptable, but encouraged by many well known scholars.
It was reported that Imam Malik once said: ‘He who practice tasawuf (sufism) without learning shari’a corrupts his deen (faith), while he who learns shari’a without practicing tasawuf corrupts himself. Only he who combines the two proves true.’
Allah knows best