23 if indeed you continue in the faith, grounded and steadfast, and are not moved away from the hope of the gospel which you heard, which was preached to every creature under heaven, of which I, Paul, became a minister.
if — expresses a confident expectation (Vine)
continue = persist in, stay with, adhere to
grounded = lay a foundation — the firmness of the foundation
steadfast = seated — the inner firmness of the building
The word “if” here is not ean, an unfulfilled, hypothetical condition used with the subjunctive mode, presenting the possibility of a future realization, but ei with the indicative, having here the idea of “assuming that you continue in the faith.” That is, continuance in the gospel as it was preached by Paul would show that the person was saved and thus would be presented holy, without blemish, and unchargeable before God. That is, Paul was here addressing truly born-again Colossians, not unsaved professors of Christianity who would follow the Colossian heresy. Heretics would not be so presented, only true believers. It is not the retention of salvation that is in the apostle’s mind, but the possession of it that would be shown by their continuance in the gospel. This is directed against the false teacher’s assurance that the gospel they had heard needed to be supplemented if they wished to attain salvation. — Ephesians and Colossians in the Greek New Testament, by Kenneth S. Wuest, pages 189-190.
There are two words translated “if” in the New Testament, but even the grammar is involved. The idea of one is “if haply, if so be; but the other is, if indeed. It is Paul’s familiar challenge; you have the negative side in 1 Corinthians 15:13: If there be no resurrection — he knows there is a resurrection, but he is challenging them:
Verse 14, If Christ be not risen, then there is no resurrection. Verse 16, if the dead rise not. Verse 17, if Christ be not raised — now he had no question about the resurrection, he knew that resurrection was a fact, but he was challenging the Corinthians.
Now that’s on the negative side. But right here in Colossians we have the positive side, for example, in Colossians 2:20, he says, If ye be dead with Christ … why, as though living in the world, are ye subject to ordinances? Now he didn’t question that they had been raised with Christ, they had been. But it’s a challenge:
If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God (Colossians 3:1).
I might illustrate it in this way. Here’s a mother, and her son has turned to be 21, and he’s bragging: “I’m 21 now, you know, and I can do what I want” and so on. And the mother says, “Well, if you’re 21, act it.” Now she didn’t have any doubt that he was 21, and yet she used the word if. She was challenging him, and Paul used it in the very same way here in Colossians 1. Christ died to reconcile you:
and by Him to reconcile all things to Himself, by Him, whether things on earth or things in heaven, having made peace through the blood of His cross. And you, who once were alienated and enemies in your mind by wicked works, yet now He has reconciled in the body of His flesh through death, to present you holy, and blameless, and above reproach in His sight (Colossians 1:20-22).
Assuming is the way he uses “if indeed,” assuming that you are still as you were when I saw you.” If they had not been, if they had departed from the faith, it would have meant only one thing: that they had never been saved in the first place, because God keeps His own. — Commentary on Colossians, by C.R. Stam, pages 86-87.