After expressing the magnitude of the greatness of Christ, Paul moves to what Christ has done for us. The gospel of Christ is truly good news to those who understand their own position before God.
Paul begins with the bad news. Once we were alienated. While we are now citizens of the kingdom of the Son, we were once aliens to that kingdom, and not only aliens, but hostile to it. As Paul states elsewhere, we were His enemies (Romans 5:10). Born into sin and depravity, we stood opposed to God.
Not only were we born into sin, but we acted upon the sin within us. As enemies of God, we opposed His rule and His commands. We are guilty not merely because we were born into sin, but because we actively sinned against the one true God.
But Christ did not leave us in our sin. He stepped into history and personally, in His own body, bore the punishment we deserved. The perfect and faithful Son paid the price for the rescue of His own enemies. And because of this rescue, He now presents us to the Father, not as the condemned rebels we once were, but as holy, blameless, and above reproach before God.
Paul calls us to remain steadfast in this gospel, strengthened by the power of Christ. Not earning our salvation, but persevering in the salvation Christ has earned for us. The One who reconciles us is also the One who strengthens us to endure.
What a great salvation this is! That the holy and faithful Son died to make His enemies pure and undefiled before God, bringing about the reconciliation of God and man through the blood of His cross.
-steve