Musar for Berakhot 18:1

The subject matter this Midrash concentrated on is the קליפה, peel, that was created by Adam's sin, which caused the brilliant light prevailing at the time of Creation to be withdrawn, and which can only be regained through efforts to refine oneself and to repair the damage done by Adam. The means to achieve such refinement is the series of exiles. Once having lived through these exiles, Israel's sins will be expiated, the Messiah will arrive and the world will once again be bathed in the brilliant light that prevailed when Adam and Eve wore clothes woven of light. The experience of the Jewish people in Egypt was of a similar nature. Israel, which still suffered from a degree of pollutants absorbed through the serpent, was cleansed and left Egypt with its head held high. All the judgments visited upon the Egyptians were in the nature of what our sages call חידוש העולם, a renewal of universal dimensions. The phenomena displayed testified to the fact that it was G–d who had created the universe and who could work His will upon it. We have explained all this in its appropriate place. G–d had already alluded to the other exiles at the time he concluded the original covenant with Abraham reported in לך לך chapter 15. The operative words at the time were: אימה, חשיכה גדולה נופלת עליו.