1 On that day king Ahasuerus gave the house of Haman, the Jews' enemy, to Esther the queen. And Mordecai came before the king, for Esther had told what he was to her. 2 And the king took off his ring which he had taken from Haman and gave it to Mordecai. And Esther set Mordecai over the house of Haman.
3 And Esther spoke yet again before the king, fell down at his feet, and implored him with tears to put away the mischief of Haman the Agagite and his plan that he had devised against the Jews. 4 Then the king held out the golden scepter toward Esther. So Esther arose and stood before the king, 5 And said, "If it pleases the king, and if I have found favor in his sight, and the thing seems right before the king, and I am pleasing in his eyes, let it be written to reverse the letters devised by Haman the son of Hammedatha the Agagite, which he wrote to destroy the Jews who are in all the king's provinces. 6 For how can I endure to see the evil that will come to my people? Or how can I endure to see the destruction of my kindred?"
7 Then king Ahasuerus said to Esther the queen and to Mordecai the Jew, "Behold, I have given Esther the house of Haman, and they have hanged him upon the gallows because he laid his hand upon the Jews. 8 Also write to the Jews, as it pleases you, in the king's name, and seal it with the king's ring, for the writing which is written in the king's name and sealed with the king's ring, no man may reverse."
9 Then the king's scribes were called at that time in the third month (that is, the month Sivan), on the twenty-third day. And it was written according to all that Mordecai commanded to the Jews, to the lieutenants, and the deputies and rulers of the provinces which are from India to Cush, one hundred and twenty-seven provinces, to every province according to its writing, to every people after their language, and to the Jews according to their writing and according to their language. 10 And he wrote in king Ahasuerus's name and sealed it with the king's ring, and sent letters by posts on horseback, and riders on mules, camels, and young dromedaries, 11 In which the king granted the Jews who were in every city to assemble and to stand for their life, to destroy, to slay, and to cause to perish all the power of the people and province that would assault them, both little ones and women, and to plunder their goods, 12 Upon one day in all the provinces of king Ahasuerus, namely, upon the thirteenth day of the twelfth month (which is the month Adar). 13 The copy of the writing for a commandment to be given in every province was published to all people so that the Jews would be ready for that day to avenge themselves on their enemies. 14 So the posts who rode upon mules and camels went out, being hastened and pressed on by the king's commandment. And the decree was given at the palace of Shushan.
15 And Mordecai went out from the presence of the king in royal apparel of blue and white, with a great crown of gold, and with a garment of fine linen and purple, and the city of Shushan rejoiced and was glad. 16 The Jews had light, gladness, joy, and honor. 17 And in every province and in every city, wherever the king's commandment and his decree came, the Jews had joy and gladness, a feast and a good day. And many of the people of the land became Jews, for the fear of the Jews fell upon them.
[v.12-13] - The Greek Septuagint has extra text in between verses 12 and 13 which contains the text of the king's letter mentioned in verse 13. You can read the text in this article.