3. The Preparation for Redemption: Genesis 12-Malachi

The entire balance of the Old Testament is about God's preparation of the world for his redemption. God calls Abraham out of heathenism into a covenant relationship with himself. And out of Abraham would come the nation Israel, and through Israel would come the Redeemer, Jesus Christ.

The Election of the Chosen People: 5 Books of Law
Genesis, Exodus, Leviticus, Numbers and Deuteronomy

In Genesis 12, God calls a man named Abram into a special covenant relationship with himself. A covenant is an unbreakable agreement which establishes a special relationship. When God called Abram, whom he renamed Abraham, he made certain wonderful promises:

I will make you into a great nation and I will bless you; I will make your name great, and you will be a blessing. I will bless those who bless you, and whoever curses you I will curse; and all peoples on earth will be blessed through you (Genesis 12:2-3)

God gives Israel the moral law in the form of the Ten Commandments. In their covenant relationship, the one true God will be their God, loving them, giving them his gracious favor and abundantly meeting their every need. In return, they pledge themselves to fidelity to Him, and the Commandments define their responsibilities toward God under the Old Covenant. Because of the sinfulness of humanity, the moral law served a critical function for their redemption. It served to make the chosen people aware of the fact that they were sinners who needed a Savior. (See Romans 3:20 and Galatians 3:24)
In addition to the moral law, God gave the ceremonial law. God ordained a system of blood sacrifices which Israel would perform in order to receive forgiveness for their sins. He established the principle that "without the shedding of blood, there is no forgiveness of sin" (Hebrews 9:22). Similarly, when God brought Israel out slavery to Egypt, he commanded Israel to sprinkle the blood of a lamb on their doorposts. The Angel of the Lord brought the judgment of death to every firstborn in Egypt, but spared the Israelites and passed over those who were covered by the blood of the lamb. Again, God established the principle of deliverance through blood. In this way God prepared the way for the coming of Jesus Christ, the Lamb of God who takes away the sin of the world.