The Gemara (Shabbat 88a) states that at Har Sinai, Hashem held a mountain over Bnei Yisrael and said, “If you accept the Torah, good for you, and if you don’t, this will be your burial site.” This highlights the idea that Bnei Yisrael were essentially forced into accepting the Mitzvot. Only at the time of Purim did we choose to observe the Mitzvot, as the Megillah (Esther 9:27) states, “Kiyemu VeKibelu Aleihem,” that the Jews resolved to observe the laws of Purim (as well as the entire Torah) for posterity.
A proof for this can be found in Sefer Hoshei’a (14:3), when Hoshea tells the Jews, “Kechu Imachem Devarim VeShuvu El Hashem,” “Take these words with you and return to Hashem.” Hoshei’a understood that Bnei Yisrael were not performing their Mitzvot with the proper intent. Only at the story of Purim did the Jews begin performing the Mitzvot completely LiShemah and not due to coercion.
At Har Sinai, Hashem’s presence was so overwhelming that we did not truly have a choice as to whether or not to accept the Torah. During the time of Achashveirosh, Hashem’s involvement in the world was far more subtle. Hashem’s limited intervention allowed us to make a legitimate choice as to whether we will follow the Torah. Moreover, at Har Sinai, we did not have a legitimate choice whether or not to accept the Torah, since we were stranded in the middle of the fierce Sinai desert, and no viable alternative existed other than to adhere to Hashem’s command. However, during the time of Purim, we had the choice of assimilating into Persian society. Hence, our choice to observe the Torah in the time of Esther and Mordechai was a legitimate and meaningful one.
May we take to heart the words “Kiyemu VeKibelu,” and may we continue to make the choice to serve Hashem out of love and not only fear.