He then wrote a book about it called Sefer Yetzira (The Book of Creation), which is actually the very first book about the wisdom of Kabbalah.
There were many more Kabbalists after him—his disciples, his sons, and his grandsons. All of then engaged in Kabbalah, until the second disclosure of the wisdom by Moses, during the exodus from Egypt. Moses was a great Kabbalist and he wrote the book of Torah for us. In it, he expressed his own revelations about the Upper World, but in a different way.
While Abraham wrote in names, Sefirot and Partzufim, Moses expressed himself in a different language—the Language of Branches. Because everything in this world comes from Above, from a Higher World, as it is written, “There is not a blade of grass below that has not an angel above it that strikes it and tells it, “Grow.” Therefore, there is a complete correlation between everything that exists in the Upper World and everything that exists in our world.
For example, in our world we have a language and denominations and names for every item we encounter. We can then take these names and seemingly go up a level, to a Higher World, and use these names to describe everything that happens in that world. That’s what Moses did when he described the Language of Branches.
Thanks to him, we now have the book of Torah. People here in this world think that it refers to worldly events, historical events, romance, journeys and other activities. But those on a Higher Plane, which Moses wished to describe, know that Moses wasn’t writing about our world, but about what is in the Upper World. He was describing the Upper Governing Higher Providence, how souls ascend and descend, their incarnations, and the entire Upper System.
Then followed The Book of Zohar (The Book of Radiance), which was to become the best-known book about the wisdom of Kabbalah, even though no one completely understands it. The Zohar is written in the language of Midrash. This is a different language than the one used by Abraham, who wrote his book in Sefirot and names. It is also a language different from that used by Moses, who wrote in the language of branches, using words of this world. The Zohar is written like a fiction. It is imaginary and poetic. It seemingly speaks of this world and the Upper World, but it’s a language of legends, called the language of Midrash.
After The Zohar, we come to the disclosure in the Middle Ages, in Safed, by the Holy Ari, Kabbalist Isaac Luria. He wrote nothing himself, but what remains of his teachings has been recorded in writing by Rav Chaim Vital, his disciple. This marks the beginning of contemporary Kabbalah.
Then came the time of Chassidism, and the evolution of the wisdom of Kabbalah in the 17th and 18th centuries, until it evolved into our contemporary, Baal HaSulam, Rabbi Kabbalist Yehuda Ashlag. Baal HaSulam wrote the commentaries to The Zohar and the writings of the Ari, and expressed Kabbalah in a contemporary language. He wrote Talmud Eser Sefirot (The Study of the Ten Sefirot) as a scientific book. It was written academically and very precisely, with a glossary, questions and answers—a complete textbook suitable for our times.