Remember, we're still in flashback mode here (everything is still taking place after the completion of the tabernacle in Exodus 40). Let's continue…
So, Moses is inside the tabernacle and God explains to him exactly how Aaron needs to set up the lamps in the tabernacle.
As usual, God is pretty specific about the design and number of these lamps. The Big Guy really has an eye for detail.
God also tells Moses to perform a purification ritual on all the Levite males so that they will be fit for service to the tabernacle.
Naturally, the ritual involves a bath and a full body shave. Because cleanliness is next to… well, you know.
Next, the whole community is told to gather around the Levites and lay their hands on them. Again, this is because God wanted these guys to stand in for everyone. No firstborn sons of Israel needed to worry about a lifetime of religious service. The Levites would do it for them.
This also has a practical purpose—it will protect the people from the plagues that God will rain down on them if they all started bumbling around the tabernacle. Honestly, it's probably best they don't go near the thing. Leave this to the professionals, Israelites.
Once the Levites are all cleansed and ready to go, God gives them to Aaron's sons so that they can assist the priests with all kinds of fancy tabernacle duties.
But there are some restrictions—only men twenty-five to fifty years old can serve the tabernacle. At fifty, every Levite is required to throw himself a crazy retirement party. (Okay, not really, but he does have to hang up his holy hat.)
Naturally, this is all done exactly as God commands. Another point for the Israelites!