Baal HaSulam, “Introduction to The Book of Zohar”, Section 58: And I have named that commentary The Sulam (Ladder) to show that the purpose of my commentary is as the role of any ladder: if you have an attic filled abundantly, then all you need is a ladder to reach it. And then, all the bounty in the world will be in your hands.
We begin our work with the construction of a group of ten people who want to become one in it. If we transform these ten people into one, then we begin to discover a higher power within them.
After we finish this work, we begin to organize a more external circle. We must include all of these people with us to be able to connect again into a complete oneness.
With the connection of the first level, we discover the Ohr (Light) haNefesh. And by attaining connection in a more external circle we discover Ohr haRuach. But this Ohr HaRuach is discovered in the more internal circle, while the Ohr haNefesh passes to the outer circle.
If we are ready to connect an even more external circle with us, then in the more external circle, we disclose Nefesh, and in a more internal circle we disclose Ruach, and in the innermost circle we disclose Neshama. (Suppose that there were 10 people in the first circle, in the second there are 100 people and in the third 1000 people). And so on, to Haya and Yechida. It follows that our advancement depends upon expanding the external circles.
Baal HaSulam called his commentary “The Ladder” because the more that we move and advance forward and include more and more new friends with us, thanks to this, we rise up the ladder and strengthen the connection between us more and more.
In this way we transform into a greater Kli in which all of the Light of NRNHY are revealed in our Kelim: Keter, Hochma, Binah, Zeir Anpin, and Malchut. And then there is one Light and one Kli connected together into a single whole and we reach adherence with the goal of creation.
Each one of these five levels, five circles, is divided into another five and another five, meaning that the Ohr NRNHY de NRNHY de NRNHY emerges, and in total 125 levels emerge. Therefore Baal HaSulam, making his commentary on the entire Zohar, on its entire height up to the completion of correction, explains how to rise to every spiritual level through connection of all the Kelim that will be discovered. Therefore he called his commentary, “The Ladder”.
From the World Zohar Week “World Zohar Convention,” Day One 2/04/14, Lesson 1