In the book of Leviticus, God establishes the rest of the Law with Moses to set Israel apart from the rest of the world as his representatives.
God made a covenant with Israel and brought his own presence to dwell with them. However, Israel cannot enter his presence because of their corruption. In response, God introduces a set of sacrifices, the priesthood, and purity laws in the book of Leviticus.
Through sacrifice, God made a way for both praise and forgiveness. The ritual sacrifices and feasts allowed Israel to remember and relate to God as his people. In order to represent the people to God and God to the people, God institutes the priesthood, a royal responsibility for Aaron and his sons (who learn the hard way to respect their calling!). God also introduces ritual and moral purity laws to help Israel see how God’s holiness affects every part of life.
The book of Leviticus concludes with a call to covenant faithfulness. Despite the sin and impurity of Israel, God made a way for sin to be covered, allowing Israel to live near God.