The number 93 is of great significance in Thelema, a religious philosophy founded by English author and occultist Aleister Crowley in 1904 with the writing of The Book of the Law (also known as Liber AL vel Legis).
The central philosophy of Thelema is in two phrases from Liber AL: "Do what thou wilt shall be the whole of the Law" and "Love is the law, love under will." The two primary terms in these statements are "Will" and "Love", respectively. In the Greek language, they are Thelema (Will) and Agape (Love). Using the Greek technique of isopsephy, which applies a numerical value to each letter, the letters of each of these words add to 93:
Other correspondences 
As salutation 
It is common for Thelemites to greet each other with "93" in person as well as in the opening and closing of written correspondence. This custom derives from Aleister Crowley's guideline that Thelemites should greet each other with the Law of Thelema by saying "Do what thou wilt shall be the whole of the law." Since saying the entire Law can be cumbersome, using 93 has become a kind of shorthand.
In informal written correspondence, one often finds the number singularly at the head of a letter, representing "Do what thou wilt shall be the whole of the Law" and in the form "93 93/93" at the end, which stands for "Love is the law, love under will." Crowley often used this form himself within his own letters.
Aleister Crowley wrote thus on the matter:
I am often asked why I begin my letters this way. No matter whether I am writing to my lady or to my butcher, always I begin with these eleven words. Why, how else should I begin? What other greeting could be so glad? Look, brother, we are free! Rejoice with me, sister, there is no law beyond Do what thou wilt!
See also 
- Skinner, Stephen (ed). The Magical Diaries of Aleister Crowley: Tunisia 1923, p. 79, n. Samuel Weiser, 1996. ISBN 0-87728-856-9
- Liber DCCCXXXVII — The Law of Liberty .
- Thelemapedia (2005). 93. Retrieved 5 April 2005.
- Crowley, Aleister. (1997). Magick (Book Four) Edited, annotated, and introduced by Hymenaeus Beta. York Beach, Maine: Samuel Weiser.
- P-Orridge, Genesis. Thee Psychick Bible: The Apocryphal Scriptures ov Genesis P-Orridge & thee Third MIND ov Psychic TV. Edited by J.A. Rapoza. San Francisco, California: Alecto Enterprises, 1994.