God is holy, and we are not. The book of Leviticus makes the holiness of God crystal clear on every page. It cries out for blood, because we need the blood of another to cleanse us of our sins.
The sacrificial system that we read about so much in the Old Testament served as a daily and annual reminder for the people of Israel, showing them their need of a better mediator than Moses and a better covenant than the old one. They needed Jesus and the New Covenant.
It is impossible for the blood of bulls and goats to take away sin (Heb. 10:4). The priest stood daily to offer the same sacrifices which “can never take away sins” (Heb. 10:11).
Jesus Christ is our High Priest who both offered himself for us on the cross as the once-for-all sacrifice for sin and who presently makes intercession for us (Heb. 7:25; 10:12). In short, the book of Leviticus is really all about Jesus.