"Speculation on the ma'aseh bereshit was given a unique form in a book, small in size but enormous in influence, the Sefer Yezirah ("Book of Creation"), the earliest extant Hebrew text of systematic, speculative thought. Its brevity - less than 2,000 words altogether even in its longer version - allied to its obscure and at the same time laconic and enigmatic style, as well as its terminology, have no parallel in other works on related subjects. The result of all these factors was that for over 1,000 years the book was expounded in a great many different ways, and not even the scientific investigations conducted during the 19th and 20th centuries succeeded in arriving at unambiguous and final results.An excerpt of: Gershom Scholem, Kabbalah, New York: Meridian, 1978 (Jerusalem: Keter Publishing House, 1974), p. 23
Sefer Yezirah is extant in two versions: a shorter one which appears in most editions as the book itself, and a longer version which is sometimes printed as an appendix. Both versions were already in existence in the tenth century and left their impreint on the different types of the numerous manuscripts, the arliest of which (from the 11th century?) was found in the Cairo Genizah and published by A.M. Habermann (1947). In both versions the book is divided into six chapters of mishnayot or halakhit, composed of brief statements which present the author's argument dogmatically, without any explanation or substantiation. The first chapter in particular employs a sonorous, solemn vocabulary, close to that of the Merkabah literature. Few biblical verses are quoted. Even when their wording is identical, the different arrangement of the mishnayot in the two versions and their resultant altered relationship one with the other color the theoretical appreciation of the ideas."