The Gemara in Masechet Shabbat gives vivid details of the awesome scene that took place on Mount Sinai when the Torah was given.
There was thunder and lightning, and the continuous sound of the Shofar. The mountain shook and the people trembled when they heard the voice of G-d.
It was no wonder that the nation accepted the observance of the Mitzvot. The mountain was placed upon them, so to speak. It was clear that there was no way they would refuse the offer to be a “kingdom of priests, and a holy nation.” Their acceptance of their special role was mainly out of fear.
The story of Purim was directly connected to the events of Mount Sinai. The name of G-d is not found anywhere in Megillat Esther. Yet, the people were united in their collective effort to repent, and reaffirm their acceptance of the Torah.
The Megillah uses the words, קימו וקיבלו, “they accepted and fulfilled.” The explanation of these two words, is that they now accepted out of love, what they had previously accepted out of fear.
This was what was missing for nearly a thousand years. There needed to be a higher level of observance than doing things out of fear. We are commanded to both fear Hashem, and to love him. Observance out of love, is a higher level of connection.
Ideally, in our personal worship of G-d, it should contain both of these elements. Hashem is the Awesome King, and we are to fear Him and the punishments described in the Torah for non-observance. But we also must see Hashem as the Benevolent Father, who deeply cares about us, and feels our pain. These two elements are what truly bring us close to Him.
We should see Purim as the holiday that opened the channels of observance of Mitzvot through love. It is a reminder that we are to be passionate in such observance. When we have both fear and love of Hashem, we are then fully equipped to fulfill our role in the world as Jews.