The Zohar, Chapter “BeShalach (When Pharaoh Sent),” Item 181: Then everything shone together because even though the light of Atik is covered in Hassadim, it contains Hochma, as well, since the Hochma in AA is necessarily received from him. Hence, the Hassadim of Atik are more important than the Hochma de AA and are regarded as containing it, and that Hochma and Hassadim shine in him together. This is why the sea made the upper laws, to drown the Egyptians and to save Israel, since the upper and lower were given into his hands. …since the crossing of the Red Sea depends on Atik.
The Upper Light comes and severs the coarse desires in us called “Egyptians” from the desires called “Isra-El” (straight to the Creator), which are ready to be corrected. This happens by the conditions of the Second Restriction (Tzimtzum Bet).
“The nations of the world” in us are all the desires that cannot be corrected until the very End of Correction (Gmar Tikkun). This includes the Klipot and all the desires that are directly connected with the Light of Hochma.
The desires of “Israel” (Yashar-Kel) include all the qualities of Bina and by their nature they belong to Galgalta Einaym. Therefore, the Light of Hochma that comes makes a split in the entire depth of the desire or vessel, separating the desires that can be corrected (the ones belonging to Galgalta Einaym that are able to become AHP de Aliya) from the desires that are completely incapable of correction. That is why the “splitting of the Red Sea” took place: to separate “Israel” from the “Egyptians.”
From the 2nd part of the Daily Kabbalah Lesson 10/27/10, The Zohar