They are two adverbs and a conjunction — once, now, and if. Yes, I know that grammar is not everybody’s cup of tea, but these three words reveal the structure of Paul’s thought in Colossians 1:21-23. It is good for us to ponder once, now, and if.
With the word “once,” Paul points to the past, the pre-christian past of his readers. They were once alienated. This is an objective statement about status outside of Christ. Christians can and should be welcoming to non-Christians in the assembly. But just as a tourists can be welcomed in a foreign country and yet not have the privileges of citizenship until they have moved from the category of aliens to citizens, the same is true for those outside of Christ.
But Paul has two more descriptions of the past: hostile in mind and doing evil deeds. The classic statement that says our way of thinking is different from God’s is Isaiah 55:8-9.
For my thoughts are not your thoughts, neither are your ways my ways, declares the Lord. For as the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts. Isaiah 55:8–9, ESV
The more alienated we are from God, the more our thinking is going to be off, and the more our thinking is off, the more our behavior will be wrong, even evil.
“Now” indicates the change in status. The Christian’s present is different from the past. Now we are reconciled to God by the death of Christ. Reconciliation means that the broken relationship that was once hostile and alienated has been made right. We have been brought near. This is done so that we might be presented holy, blameless, and above reproach before him. There is the justification sense of that. Because I am in Christ, God will say no punishment for me. There is the sanctification sense. Because I am in Christ, I am actually growing more holy in life and conduct.
Finally, there is the big “if”. Paul says that we must continue in the faith. Although translations differ here (“the faith” ESV, NASB, KJV, NKJV and “your faith” NIV), I think “the faith” is preferable, although both statements would be true. The Greek text does have the definite article (i.e., the), and it seems to link up with what was heard and proclaimed in the latter part of the sentence.
Paul wants us to be stable, steadfast, and not shifting from the faith, the apostolic message. If we do that, we will stand before God blameless and above reproach.
Paul gives us a glimpse into our past, present, and potential future with once, now, and if.