Esther 9:19-23

Therefore the Jews of the rural areas, who live in the rural towns, make the fourteenth day of the month Adar a holiday for rejoicing and feasting and sending portions of food to one another. The Feast of Purim Instituted

Then Mordecai recorded these events, and he sent letters to all the Jews who were in all the provinces of King Ahasuerus, both near and far,

obliging them to celebrate the fourteenth day of the month Adar, and the fifteenth day of the same month, annually,

because on those days the Jews rid themselves of their enemies, and it was a month which was turned for them from grief into joy, and from mourning into a holiday; that they were to make them days of feasting and rejoicing, and sending portions of food to one another, and gifts to the poor.

So the Jews undertook what they had started to do, and what Mordecai had written to them.