Counting the Levi'im
This week's parsha begins with two censuses – one where all Israel besides the tribe of Levi was counted and the other where only Levi was counted.
While the instruction to count Levi appears immediately after Israel had been counted, it is likely that the instruction to count them and the actual counting occurred simultaneously with the ret of Israel.
The purpose of both censuses is obvious. While it turned out that Israel remained in the wilderness for forty years, this was not the original plan. Israel's sojourn in the wilderness was meant to be short.
Now that the Mishkan had been built, Israel was ready to enter the Promised Land. To do this they needed to have an operational army.
Therefore, Moshe counts Israel in order to assemble an army. Therefore, Moshe is instructed: "From twenty years old and upwards, all who are fit to go out to the army in Israel, you shall count them by their legions you and Aaron" (Bemidbar 1:3).
Indeed, their formation around the Mishkan is a military formation. Israel is preparing for war.
However, they are also preparing for conquest. Once Canaan has been conquered, Israel will need to settle it. Therefore it is crucial that they know the size of each tribe so that the land can be divided since "To the large [tribe] you shall give a larger inheritance and to a smaller tribe you shall give a smaller inheritance, each person shall be given an inheritance according to his number" (ibid 26:64).
It is therefore, also obvious why Levi is not counted together with the rest of Israel. Levi does not receive any land, and does not fight for his portion is the Lord's.
So why is Levi counted at all then? Now that the Mishkan has been built, the Levi'im must be divided into groupings so that their levitical roles can be organized.
However they are counted differently. While Israel is counted from the age of twenty, Levi is counted from the age of one month. At first glance this does not make sense since their levitical duties only began once they be came 25. It would make sense to count them from that age.
The Levites were chosen to replace the firstborns: "As for Me I have taken the Levites from among the children of Israel in place of all firstborns among the children of Israel who have opened the womb, and the Levites shall be Mine (ibid 3:12).
The firstborns belong to God from the moment they are born. Therefore, they have to be redeemed. This is done after 3 days, since only then is the child considered to be a "bar kayama", a child that will live (in the ancient world newborns had a mortality rate – if an infant survived 30 days it was considered to be living child).
Now that the Levites are replacing the firstborns, they are dedicated to God from the moment they are born. Therefore, they are counted from the age of one month.
Last years' Sedra Short on Parshat Bemidbar, entitled: The Levites appears at: http://parshablog.blogspot.com/2007_05_01_archive.html.
Another Sedra Short on Parshat Bemidbar entitled: "Re’uel or De’uel?" appears at http://parshablog.blogspot.com/2006_05_01_archive.html.