The Good News of Double Imputation

"A penal death and a perfect righteousness imputed, the one for pardon and the other for acceptance - these are the things which make the Gospel glad tidings of great joy. To deny these is to deny Christ" (James Henley Thornwell, "The Necessity and Nature of Christianity").

In his comment above, Thornwell quotes the Christmas passage from Luke 2:10, when the angel proclaims to the shepherds in the fields, "Fear not, for I bring you glad tidings of great joy!" The glad tidings were that our Savior had come, the One for whom His people had been waiting since He was first foretold in Genesis 3:15. I cannot read those words without thinking of Linus, as he spoke them, in the Charlie Brown Christmas Special.

I think even that idea is ruled out now in our politically-correct society. However, even Linus did not explain why the coming of Jesus was supposed to bring us great joy. Thornwell knew, and tells us. It isn't the part that Linus told us, but the part John the Baptist told us: "Behold, the Lamb of God, who takes away the sin of the world!" (John 1:29; see also Matthew 1:21). Jesus came to take away the sins of everyone for whom He died, not just of Israel, as the Jews expected, but in all nations (cf., Matthew 28:19-20)!

That is justification! We are set free from the burden of sin and the judgment that it brings. 

However, as Thornwell notes, Jesus didn't just cancel the debt of sin, and then leave us in some neutral state. No, He also gave us His righteousness, so that we are now His holy people: "For our sake He [God the Father] made Him [God the Son] to be sin who knew no sin, so that in Him we might become the righteousness of God" (II Corinthians 5:21).