The concept of substitutionary atonement was worked out in Israel through an elaborate sacrificial system. What was required as payment for transgression against God was the life of the perpetrator. In the OT sacrificial system, God was saying to the people of Israel, “You have committed capital offenses against Me, and the law requires your death, but I will accept in the place of your death the death of a substitute, symbolized by the death of animals.”
The value of those atoning sacrifices was in the way they dramatized the authentic atonement yet to come. In other words, people were justified by believing in the promise of God by seeing those sacrifices as shadows of a future reality. They received real atonement only from Christ.
EXPIATION AND PROPITIATION
Expiation is the removal of guilt from someone. This is the horizontal dimension of atonement. Our sins are transferred to Christ, who as the Lamb of God took our guilt upon Himself (Isaiah 53).
Propitiation involves the vertical dimension of atonement. In the act of propitiation, God’s righteous wrath is appeased, and His justice is satisfied. The moral obligation that we owe for sin is paid to God, who is fully satisfied with the price that is paid by our substitute. If we do not have a substitute, then there can be no expiation and no propitiation, because we are not capable of satisfying the demands of God’s justice.
There are those who believe it is simply barbaric and prescientific to assert that a substitute had to shed his blood (give His life) to satisfy the demands of God’s justice. But let them answer this question, “What do you do with your guilt?”
The facts are: we have all done wrong. We have all sinned against God. The price of sin is to experience the curse of God. To be cursed of God is to be cut off from His presence. Christ has redeemed us from the curse of the law by becoming a curse for us (Galatians 3:13). Christ cried out from the cross, “My God, my God, why have You forsaken Me?” (Matthew 27:46). He had to be forsaken because the penalty for sin is divine forsakenness. Jesus was cut off from the land of the living on our behalf, so that we would not be cut off.
[Adapted from Everyone’s a Theologian by R.C. Sproul]