The Bible teaches that anyone who has put their faith in Jesus as their Savior has Eternal Life, and cannot lose their Salvation. Every single sin that they have committed, or ever will commit, has been paid for. Here are the 10 best verses demonstrating this from the Word of God:
Now we will go through each of these, and comment on what makes them remarkable:
John 6:39-40
39 And this is the Father's will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day.
40 And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day.
In verse 39, Jesus states that He will not lose a single one of those who the Father has given Him. Then in verse 40, He defines that group as those who believe in Jesus. This is because believers are "kept by the power of God through faith unto salvation" (1 Peter 1:5) until a fixed point in time - which we learn from verse 40, is the day of Resurrection.
This passage is also important, because it defines the "will of the Father", which sheds light on the oft-twisted passage in Matthew 7:21, where we are told that only those who "do the will of the Father" will enter the Kingdom of Heaven.
The will of the Father is that every believer is to be eternally secure, and will be raised up from the dead to live forever with God in the new creation.
1 John 5:1
1 Whosoever believeth that Jesus is the Christ is born of God: and every one that loveth him that begat loveth him also that is begotten of him.
This verse states that believers have been "born of God". It doesn't say "will be born of God", it says "is born of God", present tense. The moment one puts their faith faith in Christ to save them, they receive the new birth (John 1:12, Galatians 3:26).
This new birth is born of "incorruptible seed" (1 Peter 1:23), and "cannot sin" (1 John 3:9, 5:18). When we die, this is all that will remain, which is why we will never sin in Heaven. This nature exists, presently, in every single believer.
While we live on earth, this nature of our new birth struggles against our old nature (Galatians 5:17), which is the flesh of our old birth, something covered in-depth in an article titled Every Believer Has Two Natures. The new creature that is born of God however, is incorruptible and sinless.
The part of a believer that is even capable of sinning is not the real "them" that God sees, if they have been born again (Romans 7:14-20). It's merely a remnant of their first birth which has absolutely no affect whatsoever on their new nature from the new birth.
John 10:28-29
28 And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand.
29 My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father's hand.
Notice in verse 28 that there is not any man that can pluck a believer out of Christ's hand. The category of "any man", logically, must include the believer themselves. Verse 29 also says that we are in the Father's hand - another witness to the fact that our Salvation is guaranteed by God Almighty. Those "given" to Christ are the ones being discussed (verse 29), and as we saw in John 6:39-40, this refers to believers in Jesus.
Further, we are not only in Jesus's hand, we are a part of His hand and His body (Ephesians 5:30). For a believer to lose their Salvation would require the body of Jesus Christ to be mutilated - it cannot happen.
Ephesians 1:12-14
12 That we should be to the praise of his glory, who first trusted in Christ.
13 In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise,
14 Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory.
This passage teaches that every single believer is sealed with the indwelling of the Holy Spirit when they believe. This Holy Spirit is the "earnest" (down payment) of our inheritance, meaning that God seals us to demonstrate His faithfulness to not losing a single one of those who have put their faith in Christ.
The Bible is replete with verses teaching that the Holy Spirit lives inside of every single believer (Ephesians 4:30, Romans 8:9: 1 Corinthians 3:16, 6:19: 2 Corinthians 1:22, 5:5, etc.), and this passage shows us that we are sealed until a fixed point in time - "until the redemption of the purchased possession", which refers to the Resurrection, when we receive a new, glorified body (Romans 8:23).
Since believers are sealed with the Holy Spirit, it is God Himself that secures their Salvation. Not only are they in the Son's hand, and the Father's hand, but the Holy Sprit is in them. Their Salvation is never put in their hands to keep, because they aren't reliable. Instead, it is kept secure by the three-fold witness of each member of the Trinity.
Romans 8:38-39
38 For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come,
39 Nor height, nor depth, nor any other creature, shall be able to separate us from the love of God, which is in Christ Jesus our Lord.
Notice that the Apostle Paul says that neither "things present, nor things to come" can separate us from the love of God. There is no conceivable action done at any point, by anyone, that can separate us from the love of God.
This bears witness to the truth that once someone is "sanctified by faith" (Acts 26:18) and made holy by the payment of Jesus Christ, they are safe forever, as Hebrews 10:14 says, "by one offering he hath perfected for ever them that are sanctified". Once someone is sanctified, they are, in the sight of God, sanctified and perfected forever. The positional sanctification of the believer is irrevocable, and nothing can possibly change that.
The purpose of verses like this is to set our mind at ease, by emphasizing that God is supremely faithful, and because He loves us, we are absolutely safe. He loves us because we are in His beloved Son (Ephesians 1:6), not because of how well we perform. A believer's Salvation was never based on that to begin with.
Romans 11:29
29 For the gifts and calling of God are without repentance.
This verse states that God's gifts are irrevocable ("without repentance"), meaning they will never be snatched back from those to whom they've been given, and God will never relinquish His promise to someone. This is particularly significant, because the Apostle Paul calls Salvation/Eternal Life a "gift" no less than 7 times in the previous chapters (Romans 5:15-18, 6:23).
Furthermore, Salvation is called a "gift" in two other prominent passages of Scripture - Ephesians 2:8-9, and John 4:10. Beyond what the Scripture says about God's faithfulness, common sense stipulates that a gift that has been given to someone cannot be taken away. The definition of a gift is something given for free, to keep.
John 6:47
47 Verily, verily, I say unto you, He that believeth on me hath everlasting life.
The greatest part about the above verse is how simple and clear the Lord is, when speaking on such an important topic. He clearly states that those who believe in Him have - as a present possession - Everlasting Life.
And if a person has, right now, Everlasting Life, then how can they perish? If they ever lost it, it would not be "everlasting", as it wouldn't have lasted forever, as the time period "forever" logically includes, as a subset, all of the time remaining in one's earthly life as well.
Romans 4:4-8
4 Now to him that worketh is the reward not reckoned of grace, but of debt.
5 But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness.
6 Even as David also describeth the blessedness of the man, unto whom God imputeth righteousness without works,
7 Saying, Blessed are they whose iniquities are forgiven, and whose sins are covered.
8 Blessed is the man to whom the Lord will not impute sin.
This passage is significant, because it touches on the fact that the sole basis for our justification before God is the imputed righteousness of Jesus Christ.
The passage states that God gives this righteousness to "the one who does not work, but believes on Him who justifies the ungodly". To them, He "imputes righteousness without works". This is the solution to the problem presented in the previous chapter - "there is none righteous, no, not one" (Romans 3:10).
This understanding of justification is a powerful proof for Eternal Security. We are saved because of the righteousness of Jesus Christ imputed to our account (Romans 3:21-22). The basis for our justification is not personal to us, or our effort, or our behavior, as such things do not play a role in our justification, nor can such things ever augment the righteousness of Christ, which is the current possession of believers. For this reason, a person who has been saved for 10 minutes has the same basis for justification, to the same degree, as a believer who has lived 50 years in service to the Lord. Both only have the imputed righteousness of Christ, to justify them before a holy God (Philippians 3:9).
1 John 5:13
13 These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God.
The above verse not only establishes that believers have Eternal Life as a present possession, but also that God wants us to know this, and be confident in this fact. God says that we should "know that (we) have Eternal Life" - and why? Because we "believe on the name of the Son of God".
Obviously, if it is possible to know this, then belief must be something that a person can look back on, and know that it has taken place. Faith is not unknowable, or mysterious, or complex, and the new birth is not a lifelong process. Instead, a believer who has put their faith in Jesus Christ can know that they have done so, and know that they are secure on that basis.
John 5:24
24 Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life.
Above is another statement demonstrating that believers have Eternal Life as a present possession. And notice - they shall not - future tense - come into condemnation. Believers have Eternal Life now (John 3:36), and are not condemned now (John 3:18), but also shall not come into condemnation, in the future.
Also notice that the one who believes "is passed" from death unto life. It is described as a completed operation, not a lifelong process.
In no circumstance can believers come into eternal condemnation in the future, because such are washed clean of their sins in the blood of Christ (Revelation 1:5: 1 Corinthians 6:11). Never again can they be condemned, regardless of what takes place, because they are redeemed by the Savior.
What about murder? Paid for. Moses killed a man and hid him in the sand. Paul was an active participant in putting Christians to death when he was a leader of the Pharisees. Adultery? Paid for. David committed adultery, got the woman's husband, Uriah, drunk, and then had him killed. Lying? Paid for. Peter denied Jesus and told people he didn't even know who He was. Abraham lied multiple times and led people to believe that his wife was his sister, because he was afraid they would kill him. Idolatry? Paid for. Solomon (as far as we know) ended his life as an idolater, and he wrote three books of the Bible.
Suicide? Paid for. Sampson killed himself, and he is listed as one of the heroes of the faith in Hebrews chapter 11. Theft? Paid for. Jesus looked to the dying thief and says "today you shall be with me in Paradise". Drug and alcohol abuse? Paid for. Noah and Lot got blackout drunk, and Lot slept with his own daughters. As one can see, the Bible is not like other "holy books" which hide their heroes' sins. The Bible is brutally honest in it's depiction of even the best of men, which is why David says "every man at his best state is altogether vanity" (Psalm 39:5).
Yet despite a believer's sins, they are washed clean forever, and as far as God is concerned, they are as white as snow (Isaiah 1:18). This forgiveness was purchased by the suffering and death of Jesus Christ, and His resurrection confirmed the purchase, and secured our redemption.
We reap what we sow in this life (Galatians 6:7), and God will chasten us if we misbehave (1 Corinthians 11:32, Hebrews 12:6) just like any good father would, but as far as our eternal, judicial standing before God is concerned, we are as spotless as Jesus Christ. Our new birth that made us a son/daughter of His is, eternally speaking, all that He sees.
Blessings in this life (Psalm 1:1-3, etc.), earning eternal rewards in Heaven (1 Corinthians 3:14-15), and avoiding God's chastening here on earth, are the motivations given to a Christian to live righteously. Threatening His children with Hell is never something that God uses to "motivate" believers anywhere in either Testament, as such a thing is absurd and impossible.
Logically, if a person could lose their Salvation, then if God loved them at all, He would take them home to Heaven the moment they believed. He would not leave them in a precarious situation for decades, dangling their soul over Hell the whole time. In such a situation, living a long life would be a curse. The doctrine that one can lose their Salvation doesn't even make sense on basic logical grounds.
Anyone who has believed in Jesus Christ as their Savior has Eternal Life, and that life, by the basic definition of the word "eternal", and many Biblical proofs, can never, ever be lost.
Every Christian denomination which teaches that one can lose their Salvation is teaching a works-based Salvation message. If one's actions can cause them to lose their Salvation (or "prove they never had it" - same consequence, same emphasis), that is not Salvation faith alone. That is Salvation by faith plus behavior - works.
It is also important to understand that "faith" really just means believing something is true. Belief in Jesus is simple trust in Him, instead of oneself, for Salvation from Hell/entrance into Heaven. Beware of attempts to redefine faith to mean "works", keeping in mind the clear distinction between the two made in Romans 4:5 and Ephesians 2:8-9:
Romans 4:5
5 But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness.
Ephesians 2:8-9
8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
9 Not of works, lest any man should boast.
Once one is saved, they are always saved, and that applies even if a person stops believing altogether (2 Timothy 2:13), as believing false religions/false doctrine is a work of the flesh (Galatians 5:19-20), which any believer is susceptible to.
The teaching that one can lose their Salvation demonstrates a fundamental misunderstanding of what happened at Calvary. Jesus paid for all of a believer's sins. Once He saves a person, He doesn't need that person's help keeping them saved. Salvation is not a cooperative effort. Jesus Christ either does all of the work, or one must be their own "savior". Grace, with respect to Salvation, is completely nullified if it is conflated with work:
Romans 11:6
6 And if by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then it is no more grace: otherwise work is no more work.
Many thoughtful Christians, because they are never taught this in a clear way, live in persistent uncertainty and fear. This is why this is such a vital doctrine, and I pray that this article has demonstrated that it is also a doctrine firmly rooted in the Word of God.
I wrote a short book entitled Eternal Security - Ten Biblical Proofs, which expounds this doctrine in much greater detail. It's available to read, always for free, by clicking here.