Answer: There is hardly anything to say about the group since it is an obvious condition. If you don’t work on the connection with the group, you don’t have a spiritual vessel.
So Baal HaSulam has only several articles about the group. A Kabbalistic group is a concept known since the days of Abraham, who was the first Kabbalist who had to work in a group. Before him, there was no need for that since the idea of the connection of the souls was not revealed. The souls were so pure until then that they didn’t need to connect to one another in order to connect to spirituality.
Although we know the history of Cain and Abel, this connection is still on the level of the roots of the evil inclination. So, Abraham was the first who needed a group although he had already attained spirituality.
He was the first link in a chain of twenty generations from Adam Ha Rishon (the First Man) until Noah, and from Noah until Abraham (ten Sefirot of the Direct Light and ten Sefirot of the Reflected Light). He was the first who started to organize a group, and so he is considered the father of the nation of Israel. This nation is a Kabbalistic group.
The concept of the group was then formed, and it is impossible to reveal spirituality without it. The more we advance, the bigger the groups become. First, the groups were only a teacher and a student, as it says: “The minimum of many is two.”
There were different stories throughout the time periods in history, but the end result is they are all eventually meant to be as one. During the events before Mt Sinai, when Egypt’s desire to receive was revealed, the unity of the group of the whole Israeli nation as one group was crucial. The conditions of the gathering before Mt Sinai were the conditions of a Kabbalistic group: To be “as one man with one heart,” “each man shall help his friend,” “don’t do unto others what is hateful to you,” “love thy friend as thyself,” and “all of Israel are friends,” connected in mutual guarantee.
These are the conditions for the existence of the group because the “nation of Israel” is a Kabbalistic group.
From the 1st part of the Daily Kabbalah Lesson 4/28/13, Shamati #25