Aren't they all serving spirits, sent out to do service for the sake of those who will inherit salvation?

Nobody takes this honor on himself, but he is called by God, just like Aaron was.

Now if there was perfection through the Levitical priesthood (for under it the people have received the law), what further need was there for another priest to arise after the order of Melchizedek, and not be called after the order of Aaron?

having a golden altar of incense, and the ark of the covenant overlaid on all sides with gold, in which was a golden pot holding the manna, Aaron's rod that budded, and the tablets of the covenant;