When G-d begins to speak to the Jews at Mount Sinai, He says, “I am Hashem your G-d, Who brought you out of the land of Egypt.”
Commentaries ask, why is the Exodus from Egypt important in this context? If G-d is trying to establish His Identity and explain why Israel is now obligated to serve Him, would it not be more appropriate to say “I am Hashem your G-d, Who Created you?”
The Ohr Gedalyahu notes that the Exodus, meaning the specific phrase “going out of Egypt,” is mentioned 50 times in the Torah (as found in the Vilna Gaon, Aderes Eliyahu). This corresponds to fifty spiritual “Gates of Understanding.” When the Children of Israel were in Egypt, they descended through forty-nine “Gates of Impurity,” and G-d brought us out through each one of them.
Our Sages say (Talmud R”H 21b) that Moshe was given all fifty Gates of Understanding, save one. The Vilna Gaon adds that similarly, Moshe understood why the Torah had to mention the Exodus forty-nine times, but not this fiftieth time.
In this way, the Ohr Gedalyahu answers the question of why the Exodus is mentioned here. According to the Gaon’s interpretation, this phrase was not added in order to explain to Israel why they were obligated to serve Him, but because the Exodus itself reached its final conclusion at the moment G-d said, “I am Hashem your G-d.”
It also corresponds to the one level of understanding that none of us, not even Moshe, can truly attain.
On Shavuos, we receive the Torah anew. We realize that it is this which has set us apart as a distinct nation from the days of the Exodus, and that its greatest secrets will always remain beyond our understanding. Yet what we have in our hands can keep the greatest of minds busy for a lifetime, while elevating us to the highest heights a human being can attain.