The Light of Yetzias Mitzrayim

The reason we merit this great light each year on Pesach is because the light that was present at the time of the exodus from Egypt returns each year. At the time of yetzias Mitzrayim, Klal Yisroel suddenly jumped from the 49th level of impurity to the 50th level of kedusha. This power returns every year. Sefer Heichal Bracha (Parshas Reeh) writes that when the Jewish people left Egypt, they reached the 50th level of holiness, but they could not remain on this level for the long-term. During the days of Sefirah, they fell from this level; however, every individual Jew can reach it again each year on Pesach.