Ein-Sof, the Infinite God, has no static, definable form. Instead, the Kabbalists conceive God, the world and humanity as evolving together through, and thus embodying, a number of distinct stages and aspects, with later stages opposing, but at the same time encompassing, earlier ones. (Source)

Ein Sof and the Kabbalah

Ein Sof literally means “endless,” and is the Kabbalah term for the deity prior to his self-manifestation at the Creation of the world.
The Kabbalah is a series of theories and texts of a mystical nature, within the Jewish religion but at the limit of rabbinic orthodoxy. It was born in the Middle Ages in the French Languedoc and developed in Gerona and other provinces of Spain. Its fundamental texts are the Zohar, the Book of Creation and the Book of Clarity.

German scholar Gerhard Scholem writes in his book “On the Kabbalah and its Symbolism”: “The Kabbalah, literally tradition, that is, tradition of divine things, is Jewish mysticism.” Scholem points to the text entitled Bahir, from the 13th century, as the first Kabbalistic text. Shortly after, the Zohar, the Book of Splendor, would appear, the central text of the Kabbalistic tradition, which Scholem attributes to Moises de León, a Spanish rabbi.

Kabbalah and the Zohar

The Zohar explains the term “Ein Sof” as follows “Before He gave any form to the world, before He produced any form, He was alone, formless and resembling nothing. Who can understand what He was like before the Creation? Therefore it is forbidden to give Him any form or likeness, or even call Him by His sacred name, or name Him by a single letter or a single dot… But after He created the form of the Divine Man [ ], He used it as chariot to descend, and He wishes to be called according to His form, which is the sacred name ‘Yhwh'”.

Thus “Ein Sof is the impersonal aspect of the hidden God”, as Scholem writes, and “is not conceivable by thought” according to the medieval French rabbi Isaac the Blind.

Ein Sof and the 10 Sefirot

Scholem indicates that from here is how the notion of the 10 sefirot appears in the mysticism of the Jewish religion, which is the way in which the unknowable deity, Ein Sof, reveals itself.

To know more

Gerhard Scholem is the great Kabbalah scholar. Some of his books are:

• Kabbalah, Meridian 1974, Plume Books 1987
• Origins of the Kabbalah, JPS, 1987
• On the Kabbalah and Its Symbolism