The essence of religion is to worship Allah alone, to worship Him only as He has prescribed, and not to worship Him through religious innovations. As the Most High says:

“To test you as to which of you is best in deeds.”

Al-Fudayl ibn ‘Iyād said: “The most sincere and the most correct.” They asked, “Abū ‘Alī, what does ‘the most sincere and the most correct’ mean?”

He replied: “If a deed is sincere but not correct, it will not be accepted. If it is correct but not sincere, it will not be accepted. It must be both sincere and correct. Sincerity means that it is done for Allah, and correctness means that it accords with the Sunnah.”

What al-Fudayl stated is something upon which the leading spiritual masters agreed. Abū Sulaymān al-Dārānī said: “An insight of the kind spoken of by these spiritual masters may occur to my heart, but I do not accept it without two witnesses: the Book and the Sunnah.”

Shaykh Abū Sulaymān also said: “Someone inspired to do something good must not act upon it until he hears a transmitted report supporting it. Once he hears such a report, it is light upon light.”

Al-Junayd said: “This knowledge of ours is bound by the Book and the Sunnah. Whoever has not read the Quran and written down hadith is not qualified to speak about this knowledge of ours.”

Sahl ibn ‘Abdullāh al-Tustarī said: “Every spiritual experience unsupported by the Book and the Sunnah is false.” He also said: “Every deed founded on religious innovation is a torment to the soul, and every deed done without following the prophetic example is self-deception.”