Shabbat HaHodesh, the last of the four special Shabbatot observed in the weeks leading up to Passover, usually comes on the last Shabbat of the month of Adar. On this Shabbat, in addition to the regular parashah, we read a maftir from Exodus (12:1-20), which is about the paschal offering.
In the maftir selection, Moses and Aaron tell the people of Israel, who are still living in Egypt, to slaughter a lamb for every household. The people are commanded to take the blood of the lamb and put it on their doorposts. Then, they must roast the meat over fire and eat it. Whatever is left after the family is finished eating should be burned completely. The blood on the doorposts acts as a marker, so that when the angel of death comes to kill all of the first born men in Egypt, he knows to skip over the Israelite houses. This maftir anticipates Passover, which is only a few weeks away.
We also read a special haftarah on Shabbat HaHodesh, taken from the book of Ezekiel. In the haftarah, Ezekiel explains a new paschal offering that will be sacrificed in the future, in the time of the third Temple.
On the first day of the first month a priest will take the blood of a bull and daub it on the doorposts of the Temple, on the four corners of the ledge of the altar, and on the doorposts of the gate of the inner court. This process is to be repeated on the seventh day of the first month. Then, on the 14th day of the first month, when Passover begins, a paschal sacrifice is offered. This concludes the purification of the Temple, the priest, and the people.
Ezekiel then specifies various details of Temple purification and sacrificial offerings. This includes regulations governing entry to the inner court for the common people, and for the Israelite king.
Finally, we read rules regarding the inheritance of Israelite kings. Kings may distribute parts of their inheritance to their subjects, but these gifts revert back to the king in the Jubilee Year, so that he may pass them on to his heirs.
Pronounced: shuh-BAHT or shah-BAHT, Origin: Hebrew, the Sabbath, from sundown Friday to sundown Saturday.