Answer: The true religion is to love your friend as thyself. This is the rule that Abraham publicized in ancient Babylon, and he gathered the people around him according to this rule into a group called Israel, which means Yashar El (straight to the Creator).
Only some of the people of Babylon followed Abraham; those who had greater vessels of bestowal. All the others had vessels of receiving. This was intentional so that they would have a chance to help one another.
First the vessels of bestowal are corrected so that they can ascend to a spiritual level. When Abraham collected them, they had nothing. So first they had to go through the hardening of the heart called Egypt, that is, they don’t ascend but rather descend.
After the exodus from Babylon, they go down to Egypt, then come out of Egypt and ascend to the receiving of the Torah. They then cross the desert, build the first Temple, and fall. They ascend again to the height of the second Temple and go through another descent to the corporeal level. This is in order to be mutually incorporated with the nations of the world and get ready for the end of the correction of the world.
The whole process, starting with the exodus from Babylon and everything that follows, is in order to reach greater connection. This is what Abraham taught. The moment they started to connect, they felt that they were in a greater and greater descent.
The Light that shone on them made it possible for them to descend more and more deeply into their ego and to see that they were far from bestowal, from the Light. Therefore, they felt the gap, the delta between the state of the exile in Egypt and the level they were on when they left Babylon, and they would have remained on that level if it weren’t for the Light. This is the gap between the Light and our ego.
From the 5th part of the Daily Kabbalah Lesson 5/19/14, Writings of Baal HaSulam