The Shabbat that precedes the first of the month of Adar (or, in the case of a leap year, Adar II) is known as Shabbat Shekalim. This is the first of four Shabbats with special Torah readings all happening before Passover.
The reading for Shabbat Shekalim is found in Exodus 30:11-16, which tells the commandment of the half-shekel historically collected before Purim:
The LORD said to Moses, “When you take the census of the people of Israel, then each shall give a ransom for his life to the LORD when you number them, that there be no plague among them when you number them. Each one who is numbered in the census shall give this: half a shekel according to the shekel of the sanctuary (the shekel is twenty gerahs), half a shekel as an offering to the LORD. Everyone who is numbered in the census, from twenty years old and upward, shall give the LORD’s offering. The rich shall not give more, and the poor shall not give less, than the half shekel, when you give the LORD’s offering to make atonement for your lives. You shall take the atonement money from the people of Israel and shall give it for the service of the tent of meeting, that it may bring the people of Israel to remembrance before the LORD, so as to make atonement for your lives. (Exodus 30:11-16)
The wording in this passage is a little confusing. Is it required to collect this tax only during a census that might occur once in a lifetime, or should it be taken more often since it funds the upkeep of the Temple and its services?
This dispute was still not settled during the days of our Master, but the majority agreed that the tax should be collected to offset the damage caused to the roads and the Temple, especially during the festival days, by an influx of religious pilgrims of Diaspora Jews and God-fearers. Theophilus Lucky, in his nineteenth century Messianic Jewish publication Edut LeYisra’el, writes:
Long ago, while our forefathers were still in their own land, the holy land that HaShem gave us as an everlasting portion, they would announce about the shekalim on the first of the month of Adar.  Emissaries went out to all the habitations of Israel, announcing to the people that the time to bring the half-shekel contribution for the public offerings had come. They used the collection to purchase sacrifices that were to be brought before HaShem, and they used it to repair their road  and eradicate all [forbidden] hybrid crops from their fields.
Though the requirement for taking a Temple Tax, as it has been called, was disputable, our Messiah set an example that has far-reaching implications for his disciples who practice Messianic Judaism today. Lucky, as he often did, gave a fresh telling of this story from the Gospels:
When we remember the shekalim we also remember the miraculous thing that our Master Yeshua the Messiah performed when he paid the half-shekel, and we remember what he said. When Yeshua and his disciples came to Capernaum, the collectors of the half-shekel approached Shimon Keifa, disciple of our Master, and said, “Does your rabbi not pay the half-shekel?”
Shimon answered, “He will pay it.”
He went to the house where Yeshua was staying. When he came to the house, Yeshua greeted him, saying, “What is your opinion Shimon: from whom do the kings of the earth take their taxes? From their children or from strangers?”
Shimon answered, “From strangers.”
Yeshua said, “Then the children are exempt. Nevertheless, in order that it will not be an obstacle to them, go to the sea and throw a fishhook in it, and take the first fish that you catch, and when you open its mouth, you will find a silver shekel. Go and pay it on my behalf and yours.”
I believe this story occurred during the month of Adar. Our Master and his disciples were in Capernaum, and the emissaries came to announce the shekalim. The collectors of the half-shekel wanted to hear what the Rabbi who teaches righteousness and truth thought about the shekalim. They honored him as an instructor sent from HaShem. Because they honored him they did not desire to ask him if he would give the shekalim, so they asked his disciple instead:
Shimon answered them, “Have you not heard that our rabbi and teacher came to uphold the Torah and fulfill it, not violate it? Our Master came to fulfill all righteousness. He does not even violate the words of the scribes. Therefore he will also give the half-shekel. And you have done well in believing that he would.”
Today we sadly are not able to give the half-shekel to fund the service of the Holy Temple, but lest we forget, we give charity in the spirit of the half-shekel. On the day before Purim, we give half of the local monetary unit times three to those in need. In the United States this would be three half dollars per person. According to custom, this money should be received by the poor before Minchah on the thirteenth as, following the prayers, the scroll of Esther is read and Purim has begun.
- m.Shekalim 1:1. They would announce in all the land of Israel, and all its border cities, that everyone must bring the half-shekel that must be given in the Temple every single year, and from these shekels (shekalim) they would purchase public sacrifices that were continually offered throughout the year, from the month of Nisan until the month of Nisan the following year.
- For the good of the state and for the repairing of the world, and they were also told to repair the highways and the mikva’ot (pools for ritual immersion). Some say this was done for the sake of the Jews in the Diaspora coming to the land of Israel for the pilgrimage festivals.
- m.Shekalim 1:1.
- Matthew 17:24-27.
Source: First Fruits of Zion