During the time of the Holy Temple in Jerusalem, every year during the month of Adar, each adult male from age 20 up would give a half shekel. This was for the purpose of buying sacrificial animals for the Holy Temple for the coming year. That way, every single household in Israel had a share in the holy sacrifices, the avoda of the Holy Temple. The Torah specifically commands that the rich man shall not give more and the poor man shall not give less. This mitzva, called the machtzit hashekel, the mitzva of giving the half shekel, obligated everyone. In the list of the 613 Torah mitzvoth, this is positive mitzva #105 according to the Sefer HaChinuch.
Like the other mitzvoth that are dependent on the Holy Temple, we cannot fulfill this obligation properly until the full redemption of our people when we rebuild the Holy Temple. Rebbe Nachman of Breslev says that exile and Diaspora are prolonged and the Redemption is delayed because of the lack of emuna in the world.
We show Hashem how we yearn for His mitzvoth and for the Holy Temple by giving charity during the week of Purim to commemorate our giving of the Half Shekel.
Everyone can participate in the mitzva of giving the half shekel. There's something special here too: when a person donates the Half Shekel donation to spread emuna, he or she not only fulfills in commemorating this wonderful mitzva but also hastens the Geula - the full Redemption of our people - and therefore expedites the rebuilding of our Holy Temple. Donate to Emuna Outreach and help Rabbi Arush spread emuna around the globe.