Esther 9:20-23

20Mordecai recorded these events and sent letters to all the Jews in all the provinces of King Xerxes, both near and far, 21to establish among them an annual celebration on the fourteenth and fifteenth days of the month of Adar 22as the days on which the Jews gained rest from their enemies and the month in which their sorrow turned to joy and their mourning into a holiday. He wrote that these were to be days of feasting and joy, of sending gifts to one another and to the poor.

23So the Jews agreed to continue the custom they had started, as Mordecai had written to them.