When did we really accept the Torah?

(16) And it came to pass on the third day, when it was morning, that there were thunders and lightnings and a thick cloud upon the mount, and the voice of a horn exceeding loud; and all the people that were in the camp trembled. (17) And Moses brought forth the people out of the camp to meet God; and they stood at the nether part of the mount.

...And they stood under the mount: R. Abdimi b. hama b. hasa said: This teaches that the Holy One, Blessed be He, overturned the mountain upon them like an [inverted] cask, and said to them, 'If ye accept the Torah, 'tis well; if not, there shall be your burial.' R. Aha b. jacob observed: This furnishes a strong protest against the Torah. Said Raba, Yet even so, they reaccepted it in the days of Ahasuerus, for it is writted, [the Jews] confirmed, and took upon them [etc.]": [i.e.,] they confirmed what they had accepted long before.

...Their contention will be this: ‘Did we accept it and fail to observe it? But surely the obvious rejoinder to this their plea would be: ‘Then why did you not accept it?’ — This, then, will be their contention: ‘Lord of the Universe, didst Thou suspend the mountain over us like a vault as Thou hast done unto Israel and did we still decline to accept it?’ For in commenting on the verse: And they stood at the netherpart of the mountain. R. Dimi b. Hama said: This teaches us that the Holy One, blessed be He, suspended the mountain over Israel like a vault, and said unto them: ‘If ye accept the Torah, it will be well with you, but if not, there will ye find your grave.’)

(20) And Mordecai wrote these things, and sent letters unto all the Jews that were in all the provinces of the king Ahasuerus, both nigh and far, (21) to enjoin them that they should keep the fourteenth day of the month Adar, and the fifteenth day of the same, yearly, (22) the days wherein the Jews had rest from their enemies, and the month which was turned unto them from sorrow to gladness, and from mourning into a good day; that they should make them days of feasting and gladness, and of sending portions one to another, and gifts to the poor. (23) And the Jews took upon them to do as they had begun, and as Mordecai had written unto them; (24) because Haman the son of Hammedatha, the Agagite, the enemy of all the Jews, had devised against the Jews to destroy them, and had cast pur, that is, the lot, to discomfit them, and to destroy them; (25) but when ashe came before the king, he commanded by letters that his wicked device, which he had devised against the Jews, should return upon his own head; and that he and his sons should be hanged on the gallows. (26) Wherefore they called these days Purim, after the name of pur. Therefore because of all the words of this letter, and of that which they had seen concerning this matter, and that which had come unto them, (27) the Jews ordained, and took upon them, and upon their seed, and upon all such as joined themselves unto them, so as it should not fail, that they would keep these two days according to the writing thereof, and according to the appointed time thereof, every year; (28) and that these days should be remembered and kept throughout every generation, every family, every province, and every city; and that these days of Purim should not fail from among the Jews, nor the memorial of them perish from their seed. (29) Then Esther the queen, the daughter of Abihail, and Mordecai the Jew, wrote down all the acts of power, to confirm this second letter of Purim. (30) And he sent letters unto all the Jews, to the hundred twenty and seven provinces of the kingdom of Ahasuerus, with words of peace and truth, (31) to confirm these days of Purim in their appointed times, according as Mordecai the Jew and Esther the queen had enjoined them, and as they had ordained for themselves and for their seed, the matters of the fastings and their cry. (32) And the commandment of Esther confirmed these matters of Purim; and it was written in the book.