Esther 9:18-20

18But the Jews in Susa did not rest until the 15th day of the month. That was because they killed their enemies on both the 13th day and the 14th day. On the 15th day they ate feasts and they were very happy.

19That is why the Jews who live in towns and villages in the country have a holiday on the 14th day of Adar. On that day, they have feasts and they give gifts to each other, because they are happy.

20Mordecai wrote down all these events. He sent letters to all the Jews who were living in all the regions where King Xerxes ruled.