Introduction to Leviticus

God ordained divers kinds of oblations and sacrifices, to assure his people of the forgiveness of their offences, if they offered them in true faith and obedience. Also he appointed the priests and Levites, their apparel, offices, conduct, and portion. He showed what feasts they should observe, and at what times. He declared by these sacrifices and ceremonies, that the reward of sin is death, and that without the blood of Christ, the innocent Lamb of God, there can be no forgiveness of sins.

-- taken from Matthew Henry's Concise Commentary