There is no Tasawwuf except it is in accordance with Quran & Sunnah.
The science of the religious law (Shariah) has an internal as well as an external aspect and inculcates inward as well as outward actions. The outward actions are bodily, such as hunger, fasting, almsgiving and the like, while the inward actions, or the actions of the heart, are faith, sincerity, knowledge of God, etc.
The esoteric science signifies the science of the actions of the interior which depend on the interior organ, namely, the heart (al-qalb) and is identical with Sufism.
The inward aspect of religion is the necessary complement of the outward aspect, and vice versa. Both aspects are inherent in the Quran, in the Traditions of the Prophet ﷺ , and in Islam itself.
Abu Nasr `Abdallah b. `Ali al-Sarrâj al-Tusi
Kitab al-luma fi l-Tasawwuf
Sufism is a *science* by means of which you learn how to behave in order to be in the presence of the ever-present Lord through purifying your inner being and sweetening it with good actions. The path of Sufism begins as a science, its middle is actions and its end is divine gifts.
Ahmad Ibn ‘Ajiba
Sufism is the practical implementation of Islam.
Sufism (tasawwuf) is a knowledge through which one knows the states of the human soul, praiseworthy or blameworthy, how to purify it from the blameworthy and ennoble it by acquiring the praiseworthy [qualities], and to journey and proceed to Allah - Most High, fleeing unto Him [by taking a spiritual path - tarîq ].
Sufism is not as some people think; merely gathering together to engage in remembrance and recite litanies. What many are unaware of is that Sufism is a complete and practical method for transforming people from loathsome (i.e. causing hatred or disgust; repulsive) individuals to complete and model human beings. This is all done through having sound faith, sincere worship, good and correct actions, and virtuous character.
The Sufi is he whose language, when he speaks, is the reality of his state.
The Mustasawwif is he that seeks to become a Sufi, bi-idhni-Allah.
Sufism is the renunciation of all selfish pleasures.
The Sufi is he that has nothing in his possession nor is himself possessed by anything.
The Sufi is he that sees nothing except God in the two worlds.
Cafes in Damascus Syria 1830s Samda Kahve
The Sufi path consists in cleansing the heart from whatever is other than Allah… The Sufis are the seekers in Allah's Way, and their conduct is the best conduct, and their way is the best way, and their manners are the most sanctified. They have cleaned their hearts from other than Allah and they have made them as pathways for rivers to run, carrying knowledge of Allah.
→ He declared tasawwuf to be a fard `ayn or personal obligation upon every legally responsible Muslim man and woman, 'as none but Prophets are devoid of internal defects and diseases.'
/more: Tasawwuf Shuyukh
Al-Shafi`i (rh) said:
I accompanied the Sufis and received from them but three words:
□ their statement that time is a sword: if you do not cut it, it cuts you;
□ their statement that if you do not keep your ego busy with truth it will keep you busy with falsehood;
□ their statement that deprivation is immunity.
Al-Khidr (the Green One) c. 18 Century