Resh Lakish said "On the first of Adar, an announcement is made concerning the Shekalim." (Masechet Megillah)
The first of the Four Special Shabbatot is Shabbat Parshat Shekalim. It occurs either on the last Shabbat of the month of Shevat, or on the Shabbat which in that year coincides with Rosh Chodesh Adar, or on a Shabbat early in Adar. A special reading, taken from Parshat KiTisa (Shemot 30:11-16) is appended to the regular Torah reading.
Read full article to obtain a fascinating overview about Parshat Shekalim which will be read this coming Shabbos.