The Jews at Shushan got together on the thirteenth of Adar, one day after the decree of Haman declared that all the Jews should be killed, having defended themselves strongly and having wiped out their enemies. By the fifteenth of Adar, they celebrated a feast as a holiday, and sent presents to one another. Mordecai sent our letters to all the Jews declaring the fourteenth and fifteenth of Adar as a celebration of rest from their enemies, when sorrow turned to joy and mourning to a holiday. The Jews accepted the custom, knowing that Haman had plotted against them, casting Pur (the lot) to consume and destroy them, but Esther interceded with the king and they were saved and Haman was hanged. The Jews accepted the tradition, and Queen Esther and Mordecai sent out a second letter confirming its observance every year, and it was written in the book.
When God gives a great victory, it is important to celebrate. Testify, declare the glory of the Lord, be joyous over His great acts! When you set up landmarks in life, great memories of the greatness of God, it builds your faith and allows you to look back and think of when God performed miracles and blessings upon which you can depend when troubles come your way again. Remember, rejoice, renew your faith!