J.I. Packer gives us a beautiful description of what happens in the justification of a sinner through faith in Jesus Christ:
Justification is the truly dramatic transition from the status of a condemned criminal awaiting a terrible sentence to that of an heir awaiting a fabulous inheritance. (Knowing God, p.133)
Much more than just the commutation of sentence, more than even pardon for sin, in justification sinners are actually accepted as righteous in God’s sight. How is that possible? It is “only for the righteousness of Christ imputed to us, and received by faith alone” (Westminster Shorter Catechism, Q.33).
Part of our justification is being accepted by God. And not just being accepted, but also adopted as the children of God in Christ (1 John 3:1; Westminster Shorter Catechism, Q.34)! So instead of the well-deserved expectation of judgment and condemnation for our many sins, believers in Christ now have “an inheritance that is imperishable, undefiled, and unfading, kept in heaven for you” (1 Peter 1:4, ESV).
The Apostle Paul also writes about our inheritance in Christ:
In him we have obtained an inheritance, having been predestined according to the purpose of him who works all things according to the counsel of his will, so that we who were the first to hope in Christ might be to the praise of his glory. In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit, who is the guarantee of our inheritance until we acquire possession of it, to the praise of his glory. (Ephesians 1:11-14 ESV)
That is what makes the good news of the gospel of Jesus Christ so good! That is why the grace of God in Jesus Christ toward sinners is so utterly amazing!