In saying this, the apostle seems to have in mind the Judaisers who have come to Colossae, who believe in works, not in the atoning death of Christ. He has in mind the Gnostics who also have a kind of system of works to earn the salvation of God, which is utterly impossible.
Now we may backslide, we must make allowance for that. It maybe that a Christian has a period or a time or an event of backsliding. That is very sad, but God will bring them back to himself if they are truly converted. However, chiefly and characteristically the true Christian is an abider. He is not carried away by error and false teaching. He or she is grounded and settled in what they believe. We often have people, well not often but sometimes, and they say I have been converted. but they are very unstable. Every time you look, they have gone absent, or they have fallen again. They have gone with the crowd, or there they are back in the pub again: unstable souls. One of the great marks of salvation is stability.
From time to time somebody says, I am very worried. I never had a time that I can point to and that I can remember, they will say to me, when I was actually saved. I have trusted in the Lord, I have believed in him, he has heard my prayers, he has changed my life. But it is a great concern for me that unlike most people who give testimonies I cannot say in what month, in what week, on what day I turned and I was saved. It is either lost to my memory or I cannot pinpoint it, and that is very worrying. Do not be worried about that. Instead of asking, ‘What was the moment when I turned to Christ? If only I could capture it and see it’ ask this, ‘Has he made me stable? Have I been grounded and settled? Is the thought that I have never been saved something that fills me with horror? It is all so important to me and so precious to me.’ Nothing will take you away from trust in him. That is what the apostle is speaking about here – ‘If you continue in the faith.’ What ground of assurance this is – ‘grounded and settled, and be not moved away from the hope [anticipation of eternal life] of the gospel, which ye have heard.’