The instructions to the priesthood and prescriptions for correct temple protocol found in the book of Leviticus is laborious and wearisome to work through. It is hard to understand the God of the New Testament who is one of grace and freedom encumbering the Israelites of the Old with such huge burdens and near-impossible legalism.
But there are the occasional hints that clues us in on the basis for such elaborate institutions. Like Lev 17:11, where the LORD declares that 'the life of a creature is in the blood, and I have given it to you to make atonement for yourselves on the altar; it is the blood that makes atonement for one's life.'
Or this paradoxical declaration at the end of Lev 22, after a long list of what makes a sacrifice acceptable or unacceptable, a priest clean or unclean: 'I am the LORD, who makes you holy and who brought you out of Egypt to be your God.' Imagine that - to say that after all that has been done, none of it makes you holy - only He does.
The shedding of blood. A perfect sacrifice. The imputation of righteousness. It's all there and more.
I get the impression that the whole concept and institution of an atoning sacrifice is being systematically programmed into the consciousness and culture of the Israelites. And a perfect sacrifice at that. Truly this is God at work in history - hinting at the future when one such perfect sacrifice will come. Encrypted in this codec of levitical practice is every facet and nuance of Christ's atoning work on the Cross. It is a depth worth plumbing for such gold.