People don’t understand what The Book of Zohar actually is. When I just started studying Kabbalah, I was told that The Zohar is Musar (ethics) according to Kabbalah. Musar is a system of moral values, telling people what they should be doing and what they are forbidden from doing because they will be punished for it. These people believe that The Book of Zohar is a book of morals on a higher level, like a decree from Above.
Baal HaSulam writes that many horrible things took place in the world because The Book of Zohar was revealed before the time was right. The Zohar was only supposed to be revealed during the time of the Ari. Why is that? When a person who hasn’t been properly prepared for reading The Zohar reads it, he will not understand it correctly. He will not arrive at the same thoughts and intentions that Rabbi Shimon had when he wrote this text.
This is why Baal HaSulam added his own commentary, titled “Sulam” (Ladder), which includes a “technical” supplement to the text of The Book of Zohar. There he provides a Kabbalistic definition of every word of the Torah and explains where each word or quality is located in the structure of the soul.
This enables the person reading the text to connect both definitions, and thus to experience an inner response to what he is reading. Both worlds become revealed to him – this world and the Upper World, and he senses the Creator’s governance inside the text and inside himself.
(From Part 2 of the Daily Kabbalah Lesson, on the “Preface to the Sulam Commentary”)