One of the books written during the time of ancient Babylon describes that Abraham set his tent with treats and started inviting everyone who was interested. This is how he explained his teaching to others since back then people did not have all these modern ways of communication.
Many people stayed to continue their studies. He formed a group from them. RAMBAM (a great Kabbalist of the 12th century) wrote that Abraham took a few thousand people with him when he left ancient Babylon.
In the end, together with them, he revealed Kabbalah. He was the first one who outlined Kabbalah and gave us the understanding of it in his work The Book of Creation. He attained great heights, but he did not attain them in detail.
The whole problem in attaining the world is that the first Kabbalists were attaining the upper world in general, on a high level, while we attain it in detail. Back then egoism was underdeveloped, but today it has developed so much that it allows us to enter and research every fine part of myself and through myself, the entire spiritual space. That is, the difference in the generations’ attainment is that they were attaining in general while we attain in details. However, the Light of our attainment passes through their souls and becomes revealed in them through greater Light.
Thus, they have been always revealing Kabbalah based upon the same single principle: attracting the Light to the common desire through the group. This is the way it was during the time of Adam and through the 20 generations of Kabbalists from Adam to Abraham, which are all listed and known to us. And it has continued in the same way.
There was not a single Kabbalist who would have attained spirituality alone, suddenly realizing it and then jumping like Archimedes out of his bath tub, running and screaming about his attainment. This is impossible. This can only happen in external science, but not in Kabbalah.
From Lesson 3 Berlin Convention 1/28/2011