He made Him who knew no sin to be sin for us, that we might become the righteousness of God in Him. 2 Corinthians 5:21 (NKJV)
Since we cannot remedy our sinful state or eternal destiny through any actions of our own, we must trust in God’s provision for salvation: the person and work of Jesus Christ. When Jesus died on the cross, He bore our sins, paying our sin debt in full through the sacrificial offering of His body. The Father’s wrath and punishment for our sin were placed squarely on His Son.
That is the biblical doctrine of justification: Jesus Christ dying on our behalf and rising again to remove our guilt. We can now be reconciled to God through Christ’s substitutionary, atoning death. But we are not justified automatically. Rather, each of us must accept salvation by faith, receive the gift, and—not intellectually, but volitionally—trust in Christ.
When you, by grace through faith, believe in Christ as your Savior from sin, a supernatural change of condition occurs. At the moment of your salvation, the very righteousness of God—His holy, moral character—is imparted to you. Christ instantly and permanently transforms your sinful state.