Being a priest in the ancient world wasn't like being a priest now. Sure, there are similarities—both are community leaders and both oversee certain rituals of the religion. But we're pretty sure modern-day priests don't oversee ritual sacrifices.
For the Israelites, the priesthood had a huge role in shaping the faith of their people and of generations of believers after them. Enormous chunks of Exodus and a lot of Leviticus are believed to have been penned by priests for the masses, for their own class, and for posterity.
If these guys did in fact write large manuals on priestly life and then just inserted them into the action of the Exodus story, that means that they were keepers of the original fire and brimstone stuff. That would be like having access to every Harry Potter novel, and inserting a 200-page treatise on Quidditch fouls and play after every match Harry plays in in the original text.
Now that's power.
Because they're so powerful, the priests have their own specialized gear:
The point? The priests were supposed to look fly. You look at them and think, "Wow. These guys must really know what they're doing."
After all, if you're a priest, and you want to make sure that your class (priests) continues to have power in Israelite society, what do you do? Why, you insert descriptions of your awesome outfits into some old-school stories, of course. It's a total branding device.
So what could make a priest look cooler than nifty outfits? Two words: animal sacrifices. To all the vegans and vegetarians out there—the Biblical writers would not have been down. Animal production, consumption, and killing were a huge part of ancient life. You couldn't exactly run down to Sprout for a nice healthy salad. So when a new priest is ordained, check out what happens:
You shall bring the bull in front of the tent of meeting. Aaron and his sons shall lay their hands on the head of the bull, and you shall slaughter the bull before the Lord, at the entrance of the tent of meeting, and shall take some of the blood of the bull and put it on the horns of the altar with your finger, and all the rest of the blood you shall pour out at the base of the altar. You shall take all the fat that covers the entrails, and the appendage of the liver, and the two kidneys with the fat that is on them, and turn them into smoke on the altar. But the flesh of the bull, and its skin, and its dung, you shall burn with fire outside the camp; it is a sin offering. (29:10-14)
It might seem like a bit much to us, but it's a major symbol of power. Even today, power often comes in the form of wasting essential materials, right? Well, cattle and organized animal herding gave the ancients the ability to jumpstart civilization; wasting that material in a religious or spiritual ritual meant you were big time.
Instead of crashing up a Bentley, these guys sacrificed animals. Six of one, you know?
This whole stretch of Exodus—the legalese from 25:1-31:18—makes Aaron look as cool as humanly possible. Before, he was just Moses's sidekick, but now he and his followers get a whole section that nobody other than them (and us?) would ever care about.
As a bonus, this coolness gets passed along generation by generation:
The sacred vestments of Aaron shall be passed on to his sons after him; they shall be anointed in them and ordained in them. (29:29)
Hear that? That's hereditary lineage right there. That means Aaron's legacy will live on. Big time. Check out his "Character Analysis" for more on this guy.