The first duty of the student is to purify his soul from impure traits and blameworthy characteristics because knowledge is the worship of man’s heart as well as the prayer of his inmost self (sirr) and the oblation of his inward being before Allah. Just as prayer, which is the duty of the physical senses, is not fulfilled unless the physical body has been purified from excrements and impurities, so is the worship of the inward being as well as the reformation of the heart: they, are not fulfilled through knowledge unless they first be cleansed from impurities and uncleanliness.
- The Book of Knowledge.
