In Romans 9:15 God says, “I will have mercy on whomever I will have mercy, and I will have compassion on whomever I will have compassion.” The Common English Bible reads, “I’ll have mercy on whomever I choose to have mercy.” Clearly, God is under no obligation to forgive everyone! If God shows mercy (grants forgiveness) to some but not all then there must be a basis for His forgiveness.
According to the Bible the basis of God’s forgiveness is justice.
This is what the gospel is all about.
Because God is holy He must judge all sin. Think of it this way, if in a court of law someone who is guilty of breaking the law is set free a precedent is set that would call for all future law-breakers to be “let off the hook” of judgment. Everything would disintegrate into lawlessness. No one would be safe.
God is the holy Law-giver. He is the Judge of the universe. He must enforce His holy law. Evil must be brought into judgment. Justice must be served.
So then, how can any of us sinners be forgiven?
Paul stated that God’s actions at the cross of His Son were, “to demonstrate...His righteousness”, that is, to show forth His holy judgment upon our sin, “that He might be just and the justifier of the one who has faith in Jesus.” (Romans 3:26) God was just in judging our sin upon the cross of Jesus and is free to justify and declare as righteous sinners who put their faith in Jesus.
The only reason a holy God can show mercy to sinners and forgive their sin is because His justice for the punishment of sin was satisfied in the all sufficient sacrifice of His Son. The shed blood of Christ turned God’s throne of judgment into a mercy seat. And we all say, “Hallelujah!”