In this post I will show that the doctrine of Eternal Security is true, and an integral part of salvation through faith alone.
In Romans 8:29,30 Paul teaches:
29 ¶ For those whom he foreknew he also predestined to be conformed to the image of his Son, in order that he might be the firstborn among many brothers.
30 And those whom he predestined he also called, and those whom he called he also justified, and those whom he justified he also glorified.
Paul says that those who are justified (through faith alone in Christ alone), God “also glorified.” He speaks of the believer’s glorification in the past tense, because as far as God is concerned, for those who are justified through faith in Christ, their glorification is already accomplished.
Further, those who truly believe in Christ will not live lives of continuous, unrepentant sin, as Paul teaches in 1 Corinthians 6:9-11:
9 ¶ Do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality,
10 nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God.
11 And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.
So we see that the eternal security of the believer is a fact of Scripture. But how does this relate to salvation through faith alone? If people were saved by faith, but then had to keep commandments in order to stay saved/keep their salvation, then salvation would be by faith and works. But eternal security means that once a person truly believes in Jesus, no sin they commit can cause them to lose their salvation. Thus salvation is purely by faith, and not by works at all. And so the doctrine of Eternal Security is integral to a proper understanding of salvation by faith alone.
If you are interested in learning more about the eternal security of the believer and the truth of salvation through faith alone, I highly recommend Faith Alone, repackaged: The Evangelical Doctrine of Justification.