Do you have to be a Muslim to be a Sufi? Can anyone be a Sufi?

To set out on the path of Sufism, it is absolutely necessary to be a Muslim, for Sufism is the way of excellence in Deen, excellence in Iman and yaqeen, or certitude, and that excellence is ihsan. The belief often held in the West that Sufism is universal and a person from any religion can be a Sufi is a delusion. Without the Shahadah, correct belief, following the Shariah and the Prophetic Sunnah, no one can attain the pleasure of Allah.

If a person does not believe in any of the basic tenets of faith, for example Wahdaniyat, the oneness of Allah, and associates partners in His being or attributes or in His acts, that person is completely lost and astray. The same goes for any other tenet of Islam, such as believing in the Prophet Muhammad ﷺ as the last Prophet, or in Allah's Books or Angels or other prophets. If one does not truly believe in any of the fundamental tenets, he cannot be a Muslim.

This is proved by the hadith that Salmah bin Yazeed may Allah be pleased with him, along with his brother, went to the Beloved Prophet ﷺ and told him about their mother, who was kind and generous but died without accepting Islam. They asked the Beloved Prophet ﷺ if she would be rewarded for her good deeds in the hereafter, to which the Beloved Prophet ﷺ replied in the negative. [Musnad Ahmad 119]

Modern Sufism, the term created by orientalists, is as fake as it could be, and the concept is as Allah describes: "Deaf, dumb and blind, that they do not comprehend" [Qur'an, al-Baqarah 2:171].

Ahmad Zarruq rahimahullah, the fifteenth century Hadith scholar, states, "So there is no Sufism except through comprehension of Sacred Law or Shariáh and there is no comprehension of Sacred Law or Shariáh without Sufism, for works are nothing without the sincerity of approach." As expressed by the words of Imam Malik rahimahullah, "He who practices Sufism without learning Sacred Law or Shariáh corrupts his faith, while he who learns Sacred Law or Shariáh without practicing Sufism corrupts himself. Only he who combines the two proves true." [Ibn Ajiba, Iqaz al-himam fi sharh al-Hikam 5–6]

Modern Sufism promulgates the concept of the universal validity of all religions, which is completely against the concept of true Sufism. Islam is the final religion and the fundamental concepts of Tawheed and articles of faith cannot be compromised; Tasawwuf does not exist without the Shahadah and the Shariah. Therefore, in the words of al-Futuhat al-Makkiyya, "Do not follow anyone whose Shariáh leaves him, even if he brings you the tidings from Allah Himself." [al-Futuhat al-Makkiyya 2/364]