Esther 9:20-23

20Now, Mordecai wrote these things down and sent official letters to all the Jews in all the provinces of King Xerxes, near and far.

21He established the fourteenth and fifteenth days of the month of Adar as days they must observe every year.

22They were to observe them just like the days when the Jews freed themselves from their enemies. In that month their grief turned to joy and their mourning into a holiday. He declared that these days are to be days for feasting and celebrating and for sending gifts of food to one another, especially gifts to the poor.

23So the Jews accepted as tradition what they had begun, as Mordecai had written to them.