21 For He made Him who knew no sin to be sin for us, that we might become the righteousness of God in Him.
Verse 21 is a summary of the core message of chapter five. Verse 21 reinforces, verse 20.
He [God] made Him [Christ] who knew no sin
Christ never sinned, but God placed the sin of the world on Him at the cross. Jesus never sinned by personal experience. His sinlessness was a primary condition or qualification for His sacrifice as the lamb of God (He 4:15; 1 Pe 2:22; 1 Jn 3:5). The Old Testament lamb had to be spotless; this is no less the case for Christ’s sacrifice.
to be sin for [on behalf of] us,
Jesus took the sinners’ punishment for sin. He was sinless, yet He took the penalty for sin. He represented the sinner on the cross (Ga 3:13). The phrase “to be sin” means that Christ was the sin-Bearer. He bore the guilt of sin.
God did not make Christ a sinner on the cross; instead, He made Him pay the penalty of sin. It does not mean that He was sinful or made sinful, but He experienced the penalty of sin.
that we might become the righteousness of God
The antithesis of sin is righteousness. Jesus was made the sin-Bearer; God declared the Christian right before Himself; that is, God treats the believer as righteous, and he is righteous because Christ paid for his sin. Christians are completely free from the penalty of sin (Ro 8:3). Christ suffered condemnation so that we might be declared righteous. This is not experiential righteousness but judicial righteousness. God is just in forgiving sin and declaring those who believe as right as He is righteous positionally because of the death of Christ. They are right in God’s eyes.
God imputes His very own righteousness to the believer. “Righteousness” is the gift of a right relationship with God. Christians acquired that relationship by believing that Jesus took their sin on Himself on the cross. God adjudicated our situation because of the cross.
The “righteousness of God” is the reason that Christians have the kind of salvation they do (Ro 1:17). God’s own righteousness is at stake. If He allows sinful, unforgiven, human beings to fellowship with Him, then He would compromise His nature. By Christ’s death, our status of sin and death changed to holding the same state of righteousness that God has. This is again judicial or positional righteousness, not experiential righteousness.
in Him [Christ].
Christians stand before God in their status with Christ. God united the Christian with Him at their spiritual birth. God imputed the penalty of our sins to Christ. He also reckoned Christ’s righteousness to the believer. This is an issue of the declaration of God’s justice. God is now just in the justification of sinners because of Christ. Christians come to God with the assurance that He will accept them as they are.
Jesus took our hell that we might have His heaven.
The argument is not that His crucifixion made Christ a sinner. His sinlessness is clearly stated in this verse. He was made a sin-offering. God made Christ a curse for us (Ga 3:13). He bore our sins so that it would free God to deem us as righteous as Christ is righteous positionally (judicially).