The doctrine of “Once saved, always saved” needs to be examined in the light of the scriptures:
And you who were once estranged and hostile in mind, doing evil deeds, he has now reconciled in his fleshly body through death, so as to present you holy and blameless and irreproachable before him — provided that you continue securely established and steadfast in the faith, without shifting from the hope promised by the gospel that you heard, which has been proclaimed to every creature under heaven. I, Paul, became a servant of this gospel. (Colossians 1:21-23)
Let us hold fast to the confession of our hope without wavering, for he who has promised is faithful. And let us consider how to provoke one another to love and good deeds, not neglecting to meet together, as is the habit of some, but encouraging one another, and all the more as you see the Day approaching.
For if we willfully persist in sin after having received the knowledge of the truth, there no longer remains a sacrifice for sins, but a fearful prospect of judgment, and a fury of fire that will consume the adversaries. (Hebrews 10:23-27)
For it would have been better for them never to have known the way of righteousness than, after knowing it, to turn back from the holy commandment that was passed on to them. (2 Peter 2:21)
Not that I have already obtained this or have already reached the goal; but I press on to make it my own, because Christ Jesus has made me his own. Beloved, I do not consider that I have made it my own; but this one thing I do: forgetting what lies behind and straining forward to what lies ahead, I press on toward the goal for the prize of the heavenly call of God in Christ Jesus. (Philippians 3:12-14)