The gemara (Shabbos 88a) discusses the idea that when it came to receiving the Torah at Har Sinai, Bnei Yisrael did not really have a choice. This is symbolically represented by the idea that God held Har Sinai over their heads and gave them a choice of accepting the Torah, or dying on the spot. Of course, this did not literally happen. The idea is that at that point knowing what they knew about HaShem and in general, being who they were and where they were, there was no choice but to accept the Torah. As noted by Rav Acha bar Yaakov, this made the acceptance less than ideal. We all know that a forced agreement is not much of an agreement. Rabah answers cryptically that they accepted the Torah willingly at the time of Purim. This is a very problematic statement. Where do we see an acceptance of the Torah during the time of Purim? If anything, the Jews are beginning to assimilate. After an analysis of knaus in the Torah, I will suggest an explanation to this challenging piece of aggada.
This then, is the explanation for Rabbah's words in maseches Shabbos. The new acceptance of the Torah refers to the new approach to HaShem and his Torah. From this point forward, force no longer plays a role in Kabbalas HaTorah. It is no longer about an offer that can not be refused, but a willing and loving choice.
The only call of Mordechai and those who follow afterwards can be “Mi L'Hashem, L'HaShem”, those who are for God should turn to God. God can be found through his word and not the sword. Alternatively, only God can say “Mi L'Hashem Eilai”, all who desire My presence should turn to Me.