Adar concludes the year and provides the opportunity to make up for one’s “losses.” This is associated with the Talmud’s statement, “When the month of Adar enters, we must increase our happiness.” When you find a lost object, you are happy. This is true in the spiritual realm as well. The Talmud relates that a sage once became very happy because he remembered a certain teaching he had forgotten. Likewise, the Baal Shem Tov compared the joy experienced in Torah and Mitzvos to the joy felt by a king’s son who, after many years of being lost, becomes reunited with his father. Since Adar concludes the calendar year and brings out the principle that nothing is ever lost, it is always a month of happiness.
chabad.org
When Mordechai sent out letters to Bnei Yisrael that would prepare them to protect themselves against their enemies, he uses the word atidim/be prepared for the future. However, the word is actually written as atudim. Atudim are those goats in the herd that keep the entire herd together. What Mordechai was teaching Bnei Yisroel was that when that future day of battle against our enemies arrives, we will be successful only if we remain united.
There was even more power in the half shekel, writes the Netivot Shalom, citing the Noam Elimelech. While there is no individual who has not sinned, Klal Yisroel, the collective nation, is still considered pure. When each individual gave his personal half shekel to the whole, he became part of the collective and was again able to form the close relationship with Hakodosh Boruch Hu.
outorah.org
