Question: What are The Four Parshios?
Answer: The Sages instituted four special Torah readings on four different Shabbats during the Purim season. These readings are read as the Maftir portion in the synagogue on Shabbos morning, immediately following the weekly parsha.
1. PARSHAS SHEKALIM
Exodus 30:11-16 is read in commemoration of the Half Shekel which every Jew brought during the month of Adar, to pay for the public offerings in the Holy Temple. This portion is read on the Shabbos preceding Rosh Chodesh Adar (or Adar II in a leap year).
2. PARSHAS ZACHOR
The Shabbos immediately preceding Purim is called Shabbos Zachor. The portion of Amalek (Deut. 25:17-19) is read, since Haman was a descendant of Agag, King of Amalek. One should be very careful to listen to all the words since most halachic authorities consider it a Torah-level mitzvah to hear this portion once each year.
Zachor means to remember, and the Torah commands us to “remember what Amalek did to you on your way out of Egypt” (Deut. 25:17). It is the widespread custom for women to attend synagogue and hear the reading.
3. PARSHAS PARAH
Parshas Parah (Numbers 19:1-22) is read on the Shabbos following Purim. These verses deal with the Red Heifer used in the spiritual purification process at the time of the Holy Temple. This issue is important at this season of the year since in looking forward to Pesach, every Jew is careful to maintain spiritual purity in order to partake in the holiday offerings. Many authorities regard this reading as a Torah precept.
4. PARSHAS HACHODESH
Finally, on the Shabbos preceding Rosh Chodesh Nissan, we read the special Maftir from Exodus 12:1-20. These verses contain the commandment to make Nissan the head of all months. This was the first mitzvah given to the Jewish people while still in Egypt.