My Response: The writings of the rest of the Kabbalists are concentrated in both of them. Therefore, by studying the writings of Baal HaSulam and Rabash, we are not missing anything. First, they are the last and closest to us. Second, they are truly the modern Kabbalists of the twentieth century.
Third, all the previous Kabbalists throughout many generations are somehow gathered and concentrated in the writings of Baal HaSulam and Rabash, and so we have not lost anything.
In their writings, Baal HaSulam and Rabash relied upon the more ancient Kabbalistic sources, such as The Book of Zohar, the Sefer Yetsirah, and so forth. There are also articles that they themselves wrote. It is easier for us to read and study them.
In principle, we have no need for more than this. Also, without going beyond the framework of their writings, we can fully acquire the wisdom of Kabbalah and apply it in a way that is necessary for our correction.
Question: Baal HaSulam and Rabash are like a lens that concentrates the rays of the sun?
Answer: Yes, Baal HaSulam gathered everything that was before him for us. He explained The Book of Zohar and the writings of Ari. There was no important subject in the wisdom of Kabbalah, the wisdom of managing the world through a system of higher behavior, which he has not clarified.
Baal HaSulam explained everything, he brought the wisdom closer to us and expressed it in a language that is understandable to us. If we do not study his writings, we will actually be incapable of understanding anything in the world, its behavior, and its purpose.
From KabTV’s “Fundamentals of Kabbalah” 3/10/19