“For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God.” – 2 Corinthians 5:21 (ESV)
Here the Apostle Paul summarized the heart of the gospel, that which he stated was ‘the message of reconciliation” (v.19). This explains how sinners such as us can be reconciled to God through Jesus Christ. Two actions by God the Father upon Jesus, the Son of God resulted in the fulfillment of the promised destruction of sin in Genesis 3:15. Jesus the sinless Son of God, knew no sin was made to carry our sin on our behalf. God the Father, using the principle which is called imputation, treated Christ as if He were a sinner though He was not, and had Him die as a substitute to pay the penalty for the sins of those who believe in Him. “God was in Christ reconciling the world to Himself” v.19 “God by His own will and design used His Son, the only acceptable and perfect sacrifice, as the means to reconcile sinners to Himself.” “On the cross, Jesus did not become a sinner (as some suggest), but remained as holy as ever. He was treated as if He were guilty of all the sins ever committed by all who would ever believe, though He committed none.”*
* John F. MacArthur Jr., The MacArthur Study Bible: New American Standard Bible., (Nashville, TN: Thomas Nelson Publishers, 2006), 2 Co 5:21.