Esther 9:1, 15, 17, 19, 21

Now in the twelfth month (that is, the month of Adar) on the thirteenth day when the king’s command and edict were about to be executed, on the [very] day when the enemies of the Jews had hoped to gain power over them [and slaughter them], it happened the other way around so that the Jews themselves gained power over those who hated them.

The Jews who were in Susa also gathered together on the fourteenth day of the month of Adar and killed three hundred men in Susa, but they did not lay their hands on the plunder.

This was done on the thirteenth day of the month of Adar, and on the fourteenth day they rested and made it a day of feasting and rejoicing.

Therefore the Jews of the villages, who live in the rural [unwalled] towns, make the fourteenth day of the month of Adar a holiday for rejoicing and feasting and sending choice portions of food to one another.

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