Why was it necessary for Christ, the Redeemer, to die?
Since death is the punishment for sin, Christ died willingly in our place to deliver us from the power and penalty of sin and bring us back to God. By his substitutionary atoning death, he alone redeems us from hell and gains for us forgiveness of sin, righteousness, and everlasting life.
And you, who were once alienated and hostile in mind, doing evil deeds, he has now reconciled in his body of flesh by his death, in order to present you holy and blameless and above reproach before him.
Colossians 1:21-22
The doctrine of justification by faith lay at the heart of the gospel. This is the belief that when we place our faith in the finished work of Jesus Christ, we are more than merely forgiven. We are declared righteous. We are not merely given a clean slate to start over again, and ‘try not to mess it up this time’ — no, we are given a full account, a table-full, riches of Christ’s righteousness on our behalf. We are not merely told ‘your debts are forgiven, you may leave’. No, we are told ‘you have been adopted into this kingdom, awarded all the righteous rewards of a firstborn son, a heir-inherent.’
And while it is true, that justification is the heart of our faith, the heartbeat may well be penal substitutionary atonement. If justification is the why we can stand before a holy righteous God and not be condemned, then penal substitutionary atonement is the how. As the catechism answer above says by his substitutionary atoning death, he alone redeems us from hell and gains for us forgiveness of sin, righteousness, and everlasting life.
Penal substitutionary atonement has had its critics in the last century or so. Some criticize it as ‘cosmic child abuse’, saying ‘God the father would never pour out his wrath on his beloved Son’. In spite of that being a horrible misunderstanding of divine simplicity and the unity of the Godhead in the act of redemption, it also fails to acknowledge that Jesus Christ, God the Son incarnate, freely chose to engage in this mission. That he was not subjected to anything unwillingly. That he freely laid himself down, despite having the power to call down twelve legions of angels to deliver him from the task (Matt. 26:53). There was no cosmic child abuse. Merely Love incarnate, laying down his life for his friends (John 15:13).