When I was in college, my roommate went to a church that believed it was possible to sin in such a way that a Christian could lose his salvation. He would have been a genuine believer, then not a believer and – if he desired salvation – would need to repent, believe and be saved all over again.
When I challenged him on this belief, trying to show him it was wrong from the Bible, he was convinced. And part of his reasoning was based on what he had heard from those who believed if you ‘once saved, you were always saved.’ He said he would hear people talk about their relatives and friends who were living the worst possible lives, full of sin and depravity. And these people would say, ‘Pray they come out of that sin. I’m sure their saved because when they were 5 they said a prayer. But they need to get their life together.’
That would just infuriate my roommate. In his mind, ‘once saved, always saved’ meant you could live however you want and still be a Christian. There was no incentive to holiness or godliness. There was only an across-the-board assurance of salvation regardless of anything in their life. Although, now Jason has been convinced from the Bible that true Christians cannot lose their salvation, he had a good point in those discussions. Many fall into this trap of thinking; he had good reason to be frustrated.
Yet the author Hebrews says we are to strive for holiness without which no one will see the Lord (Heb 12:14). And the apostle Peter says, “As obedient children, do not be conformed to the passions of your former ignorance, but as he who called you is holy, you also be holy in all your conduct, since it is written, ‘You shall be holy, for I am holy.’” (1 Pet 1:13-16). Peter says if we have been adopted as God’s children, then we will act like our heavenly Father. Part of our calling to salvation is a calling to holiness.
In other words, there is no such thing as the carnal Christian. Yes, Christians are not and will not be perfect until we reach heaven. But biblically speaking, there is no such thing as a Christian who accepts Jesus as Savior but not as Lord. There is no such thing as a Christian who lives in perpetual sin.
The apostle John makes this clear when he writes, “Whoever makes a practice of sinning is of the devil, for the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the works of the devil. No one born of God makes a practice of sinning, for God’s seed abides in him, and he cannot keep on sinning because he has been born of God. By this it is evident who are the children of God, and who are the children of the devil: whoever does not practice righteousness is not of God, nor is the one who does not love his brother.” (1 John 3:8-10)
We can fool ourselves into thinking we’re okay with God. We can convince ourselves that no matter how much we sin and no matter how hard we run from God, we’re okay. We said a prayer as a child, we were confirmed when we were young, we have an emotional experience that makes me feel saved – all kinds of things. But the Bible clearly says a test of the genuineness of our faith is not a mere profession, but real perseverance. Real Christians, though they will sin and stumble, feel sorrow for their sin because they know it grieves God and betrays the work he has done for in Christ. And so they fight hard against sin. Though they may sin, they’re lives are not characterized by sin.
But what gives us the incentive to do such striving? After all, holiness is work. It’s difficult, spiritual work. And what’s to say we will even succeed? What if we fail in the pursuit of holiness? Can Christians lose their salvation? No they can’t. Though it may appear that someone was a Christians and fell away, remember that not everyone who claims to be a Christian is really a Christian. But real Christians don’t lose their salvation when they sin. The death of Christ on the cross paid for all the sins of his people – past, present, and future.
The truth of the matter is that as God’s people – as those who have placed their faith in Christ – we cannot fail. Yes, we will sin and we will stumble and we will progress in holiness more slowly at some times than at others. But the Bible makes clear that “For those whom he foreknew he also predestined to be conformed to the image of his Son” (Rom 8:29). When God chose to save humanity from their sins through the death of Christ, he didn’t just have a potential plan for salvation. The Bible says that specifically chose whom he would save. And in choosing to save, he not only predestined them for forgiveness and eternal life, but predestined them to holiness. Just as God calls his people to persevere in the faith, he is the one who is ultimately working in their life to build up their faith and keep from abandoning Christ. Ultimately God is the one at work preserving his people and ensuring their salvation.
So the same Peter who wrote strive for holiness, can also assure his readers of their salvation. “Blessed be the God and Father of our Lord Jesus Christ! According to his great mercy, he has caused us to be born again to a living hope through the resurrection of Jesus Christ from the dead,  to an inheritance that is imperishable, undefiled, and unfading, kept in heaven for you,  who by God’s power are being guarded through faith for a salvation ready to be revealed in the last time.  In this you rejoice, though now for a little while, if necessary, you have been grieved by various trials,  so that the tested genuineness of your faith—more precious than gold that perishes though it is tested by fire—may be found to result in praise and glory and honor at the revelation of Jesus Christ.  Though you have not seen him, you love him. Though you do not now see him, you believe in him and rejoice with joy that is inexpressible and filled with glory,  obtaining the outcome of your faith, the salvation of your souls.” (1 Pet 1:3-9)
Notice, the realities of the salvation come before the call to holiness. The truth of what God has done for us in Christ is what fills us with joy and gives us a lasting motivation to turn away from sin and towards God in faith. God’s grace sustains our faith so that we do not fall into persistent unbelief and forsake our salvation. The better we understand God’s grace in salvation – what was achieved for us on the cross for our life now, and our life in the age to come – the better we will feel the call of our citizenship in heaven and lose our taste for this world.