Description of Tasawwuf by Maulana Maududi-Towards Understanding Islam:
Fiqh deals with observable conduct, the fulfilling of a duty to the letter. That concerning itself with the spirit of conduct is known as Tasawwuf. For example, when we say our prayers, Fiqh will judge us only by the fulfillment of the outward requirements such as ablution, facing towards the Kabah and the timing and the number of Raka'ahs. Tasawwuf will judge our prayers by our concentration and devotion and by their effect on our morals and manners. An Ibadah devoid of spirit, though correct in procedure, is like a man handsome in appearance but lacking in character and an Ibadah full of spirit but defective in execution is like a man noble in character but deformed in appearance.
The above example makes clear the relation between Fiqh and Tasawwuf. But it is to the misfortune of the Muslims that as they sank in knowledge and character with the passage of time, they also succumbed to the misguided philosophies of nations which were then dominant, partook of them and patched Islam with their perverted dogmas.
They polluted the pure spring of Islamic Tasawwuf with absurdities that could not be justified by any stretch of the imagination on the basis of the Qur'an and the Hadith. Gradually a section of Muslims appeared who thought and proclaimed themselves immune to and above the requirements of the Shariah. These people are totally ignorant of Islam, for Islam cannot admit of Tasawwuf that takes liberties with the Shariah. No Sufi has the right to transgress the limits of the Shariah or treat lightly primary obligations (Faraid) such as daily prayers, fasting, Zakah and the Hajj. Tasawwuf, in the true sense, is an intense love of Allah and Muhammad (blessings of Allah and peace be upon him) and such love requires a strict obedience to their commands as embodied in the Book of God and the Sunnah of His Prophet. Anyone who deviates from the divine commands makes a false claim of his love for Allah and His Apostle.