Would you like to be the bearer of a radio-active vault? Touch it you die; don't carry it and you're gone. Such is the fate of the sons of Kohath, Gershon, and Merar.
The Tabernacle represents Sion. Symbolically, it is the Mountain of the Lord; his dwelling amongst men. Practically, it is the abode of the Shekinah, the holy presence. The sons of Kohath, Gershon, and Merar -- all Levites, were chosen by God for the dismantling, transportation, and rebuilding of the Tabernacle, even though these activities could be lethal.
Even danger comes knocking at your door, remember the Lord is nearby and your faith in him is all the safety you need. So it was with these Levites.
Now that the ability to move the tabernacle has been secured, the Lord turns his attention (so to speak) to the Israelite camp where He dwells, and chapters 5 and 6 are spent on the purification of the camp. By these means, God is impressing upon Israel that holiness does not abide sin.
These chapters unequivocally show he is not only interested in our salvation individually, but he is also very interested in the organization and care of the Israelite camp; a prefiguration of the Church.