Ashkenazic custom: 2 Kings 12:1-17
A new king collects taxes for the upkeep of the Temple.
On Shabbat, during the month or so around Purim and Passover, we recite four special maftir readings, called the Arba Parshiot (four Torah portions). The four Saturdays are named after their readings: Shabbat Shekalim, Shabbat Zakhor, Shabbat Parah, and Shabbat Hachodesh.
Shabbat Shekalim takes place the Shabbat prior to Rosh Chodesh Adar or on Rosh Chodesh Adar itself if it happens to fall on a Saturday. On Shabbat Shekalim we read a maftir taken from Parashat Ki Tissa (Shemot 30:11-16).
The maftir describes a census of the Israelites during the time that they were wandering in the wilderness. Instead of counting the people directly, each man over the age of 20 was commanded to contribute half a shekel toward the construction and upkeep of the mishkan, the portable sanctuary, which was used until the Temple found its permanent residence in Jerusalem. When all of the money had been collected, one could calculate how many people were wandering together in the desert.
Later, the collection of the half shekel was done annually in time for the first day of the month of Nisan; we read this maftir a month before that as a reminder.
In the haftarah, we read about King Jehoash of Judah (9th century BCE), who assumed the throne when he was only seven years old after his grandmother, the evil Queen Athaliah, had his family killed. Athaliah herself was then murdered in the subsequent revolution, but Jehoash was hidden in the Temple by the wife of the High Priest Jehoiada.
The Sephardic custom is to begin reading at the end of chapter 11, in which Jehoiada and the people of Judah go to the temple of the foreign god Baal and smash the idols there. Then they rescue Jehoash from his hiding place, and he ascends to the throne.
Sephardim and Ashkenazim alike read from chapter 12, in which King Jehoash commands that all of the money being brought to the Temple should be set aside to make repairs to the structure, which had suffered severe damage.
After 23 years, King Jehoash notices that no repairs have been made on the Temple despite his earlier decree. He summons Jehoiada, who took a box, made a hole in the top, and put it right next to the altar in the Temple.
From then on the priests dropped any money that was brought to the Temple into the box. When the box began to fill up, Jehoiada and a royal scribe counted the money and delivered it to the men who were working on restoring the Temple. The money was used to pay for the carpenters, laborers, masons, and stonecutters, as well as for supplies such as wood and quarried stone.
Just as God commanded the people to contribute money for the upkeep of the mishkan, Jehoash and Jehoiada institutionalized a system to make sure that there were sufficient funds to keep the Temple clean and beautiful.