The mystical meaning of this: “The river that came flowing out of Eden” is a reference to the flow and light of Chochma (Wisdom) Above in the World of Atzilus, which is referred to as “Eden”, in which Hashem’s Infinite Light is expressed.
Hashem’s Infinite Light is drawn forth into the entire World of Atzilus in and through this level (of Chochma/Eden), until it becomes expressed in the level of Malchus (Kingship) of Atzilus which is referred to as “the Garden”, and this is the meaning of “to give ‘water’ to the ‘Garden’,” meaning to drawn down Hashem’s life-giving Light into Malchus, which is called “the Garden”.
In that World of Atzilus, “Hashem’s Light and His Keilim are totally unified”.
Meaning, the Light adapts to the Keilm and the Keilim surrender their definition and limitation to the Light, so that they work to merge Infinite and Finite. This allows Hashem’s Infinite Light to come down to the created beings. Not only is the Light united with the Keilim, but the Keilim are able to merge together cohesively, so that the Light remains one single indivisible Light throughout all of Atzilus.
And therefore the “river” of Light in Atzilus is still “one”, since it is in the World of Hashem’s Oneness being openly expressed.
Once this “river of Light” reaches the beginning of the World of Beriah “from there it splits up,” into the level of separation and division, so that it turns into four different “rivers of Light”, since the World of Beriah is the beginning of division.
In that spiritual world the created beings first experience a feeling of division and separation between themselves and their Creator, and consequently, between themselves and each other.
Now, just like in the analogy of physical rivers, one river is not the same as another river: Neither in quality, since one river will have sweet and clear water compared to a different river; nor in quantity, since one river may run for two hundred miles and another may run for only a hundred miles or the like.
So too, the “rivers of Light” Above in the spiritual worlds are not the same:
Meaning, that many “Sparks of the World of Tohu” were drawn down and fell into this spiritual “river”, the “river” called Pishon, which is a reference to the Nile river and represents the angel -the spiritual flow of life-force- appointed over the land of Mitzrayim, more “sparks” fell there than the amount or type of “Sparks” that fell into the spiritual “river” of Bavel (Babylonia) or the other spiritual “rivers”.
Because more “sparks” fell into the spiritual life-force of Mitzrayim than into the other unholy kingdoms, the accomplishment in redeeming them was of the utmost significant. This is expressed in the fact that the exile and redemption from Mitzrayim enabled the redemption from all further exiles, including the current exile, may we merit the Redemption immediately!
