Purim is the celebration that is spoken of in the Book of Esther in the Bible. Although it is not a “GOD commanded” feast, it was established by Mordecai to observe this victory.
Est 9:20 And Mordecai wrote these things, and sent letters unto all the Jews that were in all the provinces of the king Ahasuerus, both nigh and far,
Est 9:21 To stablish this among them, that they should keep the fourteenth day of the month Adar, and the fifteenth day of the same, yearly,
Est 9:22 As the days wherein the Jews rested from their enemies, and the month which was turned unto them from sorrow to joy, and from mourning into a good day: that they should make them days of feasting and joy, and of sending portions one to another, and gifts to the poor.
A tradition of Purim is to have a costume party representing the “hidden things” in the Book of Esther. There were several things “hidden” so be sure and take a look at the link above. It is a fun way to celebrate and we always pick costumes that represent something Godly.