For that reason these days were named Purim, after pur.... In view, then, of all the instructions in the said letter and of what they had experienced in that matter and what had befallen them,the Jews undertook and irrevocably obligated themselves and their descendants, and all who might join them, to observe these two days in the manner prescribed and at the proper time each year.

The Torah says, “And Moses brought forth the people out of the camp to meet God; and they stood at the lowermost part of the mount” (Exodus 19:17). Rabbi Avdimi bar Ḥama bar Ḥasa said: the Jewish people actually stood beneath the mountain, and the verse teaches that the Holy One, Blessed be He, overturned the mountain above the Jews like a vat, and said to them: If you accept the Torah, excellent, and if not, there will be your burial. Rav Aḥa bar Ya’akov said: From here there is a substantial caveat to the obligation to fulfill the Torah. The Jewish people can claim that they were coerced into accepting the Torah, and it is therefore not binding. Rava said: Even so, they again accepted it willingly in the time of Ahashverosh, as it is written: “The Jews ordained, and took upon them, and upon their seed, and upon all such as joined themselves unto them” (Esther 9:27), and he taught: The Jews ordained what they had already taken upon themselves through coercion at Sinai.

Moses went and repeated to the people all the commands of Hashem and all the rules; and all the people answered with one voice, saying, “All the things that Hashem has commanded we will do!”Moses then wrote down all the commands of Hashem....Then he took the record of the covenant and read it aloud to the people. And they said, “All that Hashem has spoken we will faithfully do! (lit. "we will do and we will hear")

(4) Among the paths of repentance is for the penitent to...
c) to separate himself far from the object of his sin; d) to change his name, as if to say "I am a different person and not the same one who sinned;"...
e) to change his behavior in its entirety to the good and the path of righteousness...