Esther 9:20-28

And Mordecai wrote these things and sent letters to all the Jews, near and far, who were in all the provinces of King Ahasuerus, to establish among them that they should celebrate yearly the fourteenth and fifteenth days of the month of Adar, as the days on which the Jews had rest from their enemies, as the month which was turned from sorrow to joy for them, and from mourning to a holiday; that they should make them days of feasting and joy, of sending presents to one another and gifts to the poor. So the Jews accepted the custom which they had begun, as Mordecai had written to them, because Haman, the son of Hammedatha the Agagite, the enemy of all the Jews, had plotted against the Jews to annihilate them, and had cast Pur (that is, the lot), to consume them and destroy them; but when Esther came before the king, he commanded by letter that this wicked plot which Haman had devised against the Jews should return on his own head, and that he and his sons should be hanged on the gallows. So they called these days Purim, after the name Pur. Therefore, because of all the words of this letter, what they had seen concerning this matter, and what had happened to them, the Jews established and imposed it upon themselves and their descendants and all who would join them, that without fail they should celebrate these two days every year, according to the written instructions and according to the prescribed time, that these days should be remembered and kept throughout every generation, every family, every province, and every city, that these days of Purim should not fail to be observed among the Jews, and that the memory of them should not perish among their descendants.