In the simplest possible terms, the biblical doctrine of penal substitution holds that Jesus’ sacrifice on the cross takes the place of the punishment we ought to suffer for our sins. As a result, God’s justice is satisfied, and those who accept Christ can be forgiven and reconciled to God.
The word penal means “related to punishment for offenses,” and substitution means “the act of a person taking the place of another.” So, penal substitution is the act of a person taking the punishment for someone else’s offenses. In Christian theology, Jesus Christ is the Substitute, and the punishment He took (at the cross) was ours, based on our sin (1 Peter 2:24).
According to the doctrine of penal substitution, God’s perfect justice demands some form of atonement for sin. Humanity is depraved, to such an extent that we are spiritually dead and incapable of atoning for sin in any way (Ephesians 2:1). Penal substitution means Jesus’ death on the cross propitiated, or satisfied, God’s requirement for justice. God’s mercy allows Jesus to take the punishment we deserve for our sins. As a result, Jesus’ sacrifice serves as a substitute for anyone who accepts it. In a very direct sense, Jesus is exchanged for us as the recipient of sin’s penalty.
Penal substitution is clearly taught by the Bible. In fact, much of what God did prior to Jesus’ ministry was to foreshadow this concept and present it as the purpose of the Messiah. In Genesis 3:21, God uses animal skins to cover the naked Adam and Eve. This is the first reference to a death (in this case, an animal’s) being used to cover (atone for) sin. In Exodus 12:13, God’s Spirit “passes over” the homes that are covered (atoned) by the blood of the sacrifice. God requires blood for atonement in Exodus 29:41–42. The description of Messiah in Isaiah 53:4–6 says His suffering is meant to heal our wounds. The fact that the Messiah was to be “crushed for our iniquities” (verse 5) is a direct reference to penal substitution.
During and after Jesus’ ministry, penal substitution is further clarified. Jesus claims to be the “good shepherd” who lays down His life for the sheep in John 10:10. Paul, in Romans 3:25–26, explains that we have the righteousness of Christ because of the sacrifice of Christ. In 2 Corinthians 5:21, he says that the sinless Christ took on our sins. Hebrews 9:26 says that our sins were removed by the sacrifice of Christ. First Peter 3:18 plainly teaches that the righteous was substituted for the unrighteous.
There are quite a few different theories about how, exactly, Christ’s sacrifice frees us from the penalty of sin. Penal substitution is the most logically and biblically sound view.