Numbers 1-4: In Order to Move

It is now a month after the temple has been assembled in the Desert of Sinai and God tells Moses to number the people.  The tribes were numerous, but they were not numbered so their strength could be verified.  They were numbered so they could be spread out surrounding the tabernacle as they moved forward from the desert to the promised land.  Each family would camp under their family banner in their assigned location in relation to the tabernacle of God, the place where God's presence would dwell as they made their journey.  God would go with them as Moses had requested.

"Now therefore, I pray, if I have found grace in Your sight, show me now Your way, that I may know You and that I may find grace in Your sight. And consider that this nation is Your people.”
And He said, “My Presence will go with you, and I will give you rest.”
Then he said to Him, “If Your Presence does not go with us, do not bring us up from here.  For how then will it be known that Your people and I have found grace in Your sight, except You go with us? So we shall be separate, Your people and I, from all the people who are upon the face of the earth.”
 So the LORD said to Moses, “I will also do this thing that you have spoken; for you have found grace in My sight, and I know you by name.” Exodus 33:13-17 NKJV

But this God who went with them was a Holy God and the ones who served him had to be holy and set apart.  That is why the Levites were not numbered with the rest of the tribes.  The Levites, which included Moses and Aaron, were numbered and assigned duties by clan.  The descendants of Kohath were to carry those things in the Tent of Meeting, The Gershonites were to carry the Curtains and coverings of the Tent,, and the  Mearites were to carry the frames of the Tent.  Not only were the clans assigned specific tasks, but they were assigned specific locations in regards to the tabernacle.  The three clans of the Levites were each assigned a different side of the tabernacle were they should camp, and Moses and Aaron and their sons were assigned to the fourth side.  Thus the temple of God was surrounded first by the Levites who had been consecrated to him and then by the people as they set out.  They were surrounding God's place, protecting it from the enemies, and in return, God was surrounding them.