Vayedaber Hasaehm el Moshe v’Aharon leimor. Ish al diglo, b’osos l’beis avosam, yachanu b’nei Yisrael mineged, saviv l’ohel moed yachanu ... and Hashem spoke to Moshe and Aharon saying. Every person under his flag, with signs according to their paternal households, the children of Israel shall encamp, around the the tent of meeting they shall encamp (ibid. 2:1-2)
Rav Hirsch points out that this seemingly simple set of commands contains a number of elements that deserve consideration. The first command, the instructions to the tribe of Levi to separate themselves from the rest of the nation and encamp around the tabernacle, was given to Moshe alone [see 1:48] whereas the parallel command to the rest of the nation to encamp on all sides of the mishkan was delivered to Moshe and Aharon [see 2:1]. Additionally, the command to the tribe of Levi instructing them to make their encampment as a buffer between the people and the holy area refers to the place as mishkan ha-eidus - the tabernacle of testimony. The command to bnei Yisrael, on the other hand, instructing them to place their tents around this area so as to serve as a front line of defense, refers to the place as ohel moed - the tent of meeting. Obviously, there must be significance in a] adding Aharon and b] using different terms to refer to the same place.
Rav Hirsch explains that the Torah differentiates between instructions that were given as a means of creating the fabric of Jewish life and those laws that were more philosophical in nature and therefore required more instruction. The separation of the tribe of Levi from the rest of the nation was evidenced in two ways. They enjoyed an elevated status [they were supported by ma’aser and in the case of the kohen section of the tribe were subject to additional laws pertaining to their requirement to be kodesh - e.g., tumah and the specific laws as to who they were permitted to marry] and they were not to be part of the encampment of the other tribes. This type of command is given to Moshe alone, for it is given to create a fact of Jewish life and does not need to be explained. The division of the tribes into separate camps, however, and the decision as to the makeup of these four camps, entailed further instruction and elucidation. Surely the tribes would ask why they were paired with each other and there would always be contention. Moreover, the very division of the people into separate camps would seem to be questionable. At Har Sinai the people had encamped as one nation - k’ish echad im lev echad - like a single person with a single heart. And now they were being divided into separate encampments based on tribal and familial divisions, hardly a recipe for the creation of a united nation. This change required the assistance of Aharon, who together with Moshe could instruct the people as to the importance of separate but equal encampments.
This might explain the change from mishkan ha-edus used in regard to the levi’im and ohel moed when speaking to bnei Yisrael. The Tabernacle served a dual role - it was both the unifying factor for the people, the common denominator that united them as a people, as well as the repository of the luchos which testified to the unique role of am Yisrael among the nations as recipient of the Torah. As long as the entire nation encamped around the Tabernacle, they demonstrated that despite individual differences, they viewed themselves as a people with a shared destiny. In this regard it was the ohel moed - the tent of meeting - for it was there that the different factions met to be instructed in the law that bound them all. As pertains to the levi’im, however, it was mishkan ha-edut - the place of restricted access - for it was here that the document - the luchos - that set am Yisrael apart from the other nations was stored. Access to the repository of am Yisrael’s contract of separation was severely restricted [see 1:53] and was guarded by the levi’im - the tribe that had been separated from the others.
Rav Yaakov Kaminetski, zt”l, adds an interesting observation in this connection. Why, he asks, was the division of am Yisrael into separate encampments delayed until after the revelation at Sinai. If the optimal way of life for the nation is division into separate units so as to preserve the unique characteristics and traits of the individual rather than establishing a single nation, should this not have taken place before Sinai? Haven’t we been taught that am Yisrael is meant to be a confederation of individual tribes, each making their separate contribution to the nation, while at the same time maintaining their unique character traits [see Yaakov’s berachos at the end of Bereishis].
Rav Yaakov answers that the preservation of the individuality of am Yisrael is only possible if they share an eternal mission. Once they are united in a common cause, they can go about accomplishing their manifest destiny in the manner that suits them best. They can add their own nuances and flavorings once the commonality of purpose - the fulfillment of Torah and mitzvos - is agreed upon by all, at the same time and with the same level of acceptance.