During the period of time between the destruction of the First Temple and the building of the
Second Temple, the Jews came very close to being annihilated because of the evil scheming of
Haman with the King of Persia, Achashverosh.
Because of the clandestine intervention of Hashem, using Queen Esther and her uncle
Mordechai as His messengers, the Jews were spared, and instead the nation of Israel was
able to avenge themselves against their enemies. In order to commemorate these miraculous
turn of events, we celebrate Purim on the 14th of Adar (and in walled cities such as Jerusalem,
on the 15th of Adar) with feasts, sending gifts of food to our friends and the needy, and with
the reading of the Megilla, the story of Purim.
The Fast of Esther is held on the day before Purim. We fast the whole day in order to
commemorate the fast that Esther fasted before she went before the King Achashverosh to
plead for mercy for the Jews. On this day we remember the dire situation that the Jews were
faced with in those days and many times throughout history.