The Zohar ("Radiance") is the greatest classic of Jewish mysticism. It is a mystical commentary on the Torah, written in Aramaic, and is purported to be the teachings of the 2nd century Palestinian Rabbi Shimon ben Yohai. Legend relates that during a time of Roman persecution, Rabbi Shimon hid in a cave for 13 years, studying Torah with his son; During this time he is said to have been inspired by God to write the Zohar. However, there is no real mention of this book in any Jewish literature until the 13th century. In the 13th century, a Spanish Jew by the name of Moshe de Leon claimed to discover the text of the Zohar, and the text was subsequently published and distributed throughout the Jewish world.
In the mid 20th century the historian Gershom Scholem offered persuasive evidence that de Leon himself was the most likely author of the Zohar. Among other things, Scholem noticed the Zohar's frequent errors in Aramaic grammar and its suspicious traces of Spanish words and sentence patterns. This finding is still disputed by many Orthodox Jews. Although de Leon apparently wrote the text, the content of the book is not fraudulent. Parts of it may be based on older works, and it was a common practice to ascribe the authorship of a document to an ancient rabbi in order to give the document more weight. No doubt Moshe de Leon truly considered himself inspired to write this text.
The Zohar contains and elaborates upon much of the material found in other Jewish mystical texts such as the Sefer Yetzirah and the Sefer Bahir, and without question is the Kabbalistic work par excellence.