The book of Leviticus is a continuation of the Exodus story line, where the book of Exodus ended with instructions for where to worship (i.e. the tabernacle), Leviticus instructions for how to worship God. Thus, it focuses on the regulations for acceptable sacrifices; the priesthood; issues of cleanliness and holiness.
While the book may seem strange to us as modern readers, it is noteworthy that animal sacrifices were commonly practiced in ancient Mesopotamia in a way similar to that of Israel. They were done to provide fellowship with the deity, to appease and secure divine favor from the gods. However, certain differences exist between the Israel and these surrounding nations of the Ancient Near East. They are:
1) Animal sacrifices were used by the surrounding nations as a means of predicting the future actions of the gods by ‘reading’ the entrails of the dead animal. Such practices were absent in Israel
2) Israel’s sacrificial system is linked to the covenantal relationship with God, who called and delivered them out of Egypt to be His own people. The surrounding nations have nothing comparable
3) Israel’s sacrificial system is centered upon the holiness of God, with its direct implications on the right way to worship and live as God’s people. Israel’s neighbors had no such concept. In fact, sexual perversion and defilement formed part of their pagan worship and daily living
Notice that the chapters 1-7 corresponds to 26-27; 8-10 corresponds to 23-25; 11-15 corresponds to 17-22. The middle section of chapter 16, Day of Atonement, being the climax. As Bible teacher David Pawson illustrates with the above diagram, the two sections of the book of Leviticus pivots around the Day of Atonement, with the first half emphasizing our way to God and the second half emphasizing our walk with God.
1) God is holy
2) Way to God
3) Walk with God
The message of holiness pervades the whole book of Leviticus. Holiness means separation. It means that which is set apart from the common and ordinary, so that it can be set apart for a purpose or person.
Two key verses are noteworthy in Leviticus:
‘Be holy because I, the LORD your God, am holy’ (Lev 11:44-45; 19:2; 20:7, 26)
‘I am the LORD, who makes you holy’ (Lev 20:8; 21:8; 22:9, 16, 32)
The statement: God is holy. It constitutes the deepest and innermost nature of God. It speaks of God being different and separate from the creation He as made. He is ‘one-of-a-kind’, where He alone is immortal, all-powerful, all-wise, all-present and morally pure. Therefore, His people and everything (i.e. priests, animals, altars, pots and pans etc.) that is employed in offering Him worship must be holy.
The command: therefore be holy. It is a command for everyone who would be God’s people. When that holiness is breached, the seriousness of the offence is repaired only through the offerings of sacrifice. Not only is this holiness portrayed in their worship but in their daily practical living and relationships.
The promise: I am the LORD, who makes you holy. Although the call to holiness is high and awesome responsibility, God aids us in the process. He who set Israel free from bondage in Egypt is also the One who would continually transform them by His gracious workings into His holy people. Christian believers, no less than Israel, who have been set free by God from sin, are confronted with His holiness and the command to be holy, but also aided by the promise of the Holy Spirit, who continues the work of transforming us more and more into His likeness, as we yield ourselves to Him.
 Diagram is adapted from, Unlocking the Bible, by David Pawson, p136.
 Unlocking the Bible, by David Pawson, p137.