On the sixth day of Sivan, the entire nation of Israel assembled at the foot of Mount Sinai. There G-d chose us as His people and we committed ourselves to observe the laws of life as outlined in His Torah.
The Talmud points out, however, that nearly one thousand years were to pass before our covenant with G-d was sealed. It was with the events of Purim, that our acceptance of the Torah was established upon an unshakable foundation.
At Sinai, we had no choice. Faced with such an awesome revelation of the divine truth, one could hardly doubt or disagree. In effect, we were forced to accept the Torah; overwhelmed and completely enveloped by the divine reality, we could not but commit ourselves to our divinely ordained mission and role.
But a thousand years later, during the events of Purim, we, the Jewish nation, reaffirmed this commitment under entirely different conditions. The divine presence did not hover over us, compelling us to recognize its truth. On the contrary: the divine face was hidden. As the name of G-d is not even mentioned once in the entire Megilla, the book of Esther. We were able to accept the divine law without any hint of coercion for Above. As stated in the words of the Book of Esther, they, "established and accepted" - meaning, says the Talmud, that they established as valid and incontestable that which they had accepted earlier at Sinai.
We were on our own, our commitment to G-d deriving wholly from within, from an inner choice to cleave to Him.