First, there exist numerous warning passages throughout the text that address both the peril of passively drifting away and actively persisting in rebellion against Christ and the gospel. These warnings all speak of the possibility that one who now believes will not be saved if he or she either drifts away or turns away deliberately (there is no distinction in Hebrews between the two paths for rejecting Christ as Lord).
The solution is to “pay closer attention to what you have heard” (2:1), to meet the gospel that is heard with faith (4:2), to “not harden your hearts” (3:8), to “take care lest their be any among you with an evil, unbelieving heart” (3:12), to “fear” (4:1), to “be diligent to enter God’s rest (4:11), because if we do not we will not escape from a “just retribution” (2:2–3), fall, not enter into His rest (4:1), and be incapable of repentance once again (6:4-8; 10:26-27).
So the question becomes, If the believer has been chosen by God before the foundation of the world to be saved, and no one ever becomes unsaved, why does the author present these warnings in the first place? In other words, there is no possibility for the Christian to lose his salvation, so why paint it this way?
Well, in light of what we spoke about yesterday, there is, in fact, a possibility that a person loses his salvation (from our perspective), and so the passages are being spoken from our perspective. This is very important to understand, from our perspective, we can lose our salvation. We can stop believing. We can let go of the faith. We can do this, because we are choosing to believe and hold on, so we can choose to not believe and let go. Again, this is the view from below. It is our experiential view, and that is what the author here is addressing.
But why bother if all Christians are going to be saved anyway? Because salvation is brought to the Christian through the means of his active participation in believing. God doesn't just decree that we will be saved and zap us into heaven. We are regenerated to believe through the urging of the Holy Spirit through the Word of God. In other words, our decision to believe is the means chosen by God to save us. Hence, we must be convinced by the Holy Spirit via the Word to believe.
This brings us to the next point. If we have to be convinced by the Holy Spirit via the Word to initially believe, we also need to be convinced by the Holy Spirit via the Word to keep believing. This is why the preached Word of God (via the Church) is so vital in a Christian's life, and without it, one falls away from the faith very quickly. What the warning passages in Hebrews amount to, then, is the Holy Spirit's method of convincing us to keep holding onto Christ.
But there is even more of a brilliance to this that often goes unnoticed. God has chosen our decision to have faith as the means through which He will save us, so that means that we must choose to keep that faith, to continually exalt Christ as Lord in our lives. What this means is that we must not turn from it, either slowly or abruptly, because of other concerns in life or death.
This brings us to the warning passages themselves. What is their function then? As we've already discussed, the speak with the perspective from below, but they do so in order to push us to the means of our salvation, i.e., faith.
Let me explain it this way. If you've ever seen the movie, "The Matrix," and liked it a lot, then you're cool. But beyond that, there is a great scene where Neo goes into see the Oracle, and as he enters the room, she says to him, "Don't worry about the vase." He then turns around to see what she is talking about, and in so doing, he knocks over the vase and breaks it. He then asks her, "How did you know?" She replies, "Ohh, What's really going to bake your noodle later on is, would you have broken it if I hadn't said anything?"
I love this scene because it brings out the purpose of Scriptural warnings well. Our salvation is through the convincing of the Holy Spirit through the Word of God, and if God had not convinced us through the Word of God, we would not have believed. Hence, the warning passages speak with the voice the view from below precisely because it is one of the means through which God convinces us to believe and to hold onto that faith.
In other words, we can ask God, "How did you know I would be saved," but He could just respond to us and say, "What's really going to bake your noodle later on is, whether you would have believed had I not said anything, had I not warned you that you could be lost, had I not said things in the way that I did."
Hence, the warning passages warn us of a reality within our experience: we might lose our faith and not be saved; but the irony is that these warnings are only effective in stirring those who are truly saved to keep the faith. In other words, they sober up true believers, and cause them to hold on tighter than before to Christ, not knowing if they have been elected for salvation or not. In this way, they become the vehicle through which God drives us to our destination, a destination of which He was always in control.
And that must be understood here. As I said yesterday, the view from below is always to be understood in light of the view from above. That's true in Hebrews as well. The author believes that it is God who is in sovereign control of our faith in the ultimate sense, so he is not departing from that, or advocating an alternate Wesleyian theology. He plainly says that it is Christ who is the "Author and Completer of our faith" (12:2). He is the one who authors our faith so that God can bring many sons to glory (2:10). Notice, God brings them there. They do not bring themselves. Even in the most terrifying of warning passages, where we are told that repentance is not possible for those who reject the faith, the idea is that God withholds repentance from them, showing that He is the One who grants or does not grant repentance that leads to faith. And in 13:21, it is God who equips us with every good thing to do His will, working in us that which is pleasing in His sight.
Hence, as Ellingworth notes,
The author . . . maintains a balance between describing his readers as sharing in Christ and in the blessings of faith (3:1, 14) and severely warning them of the dangers of apostasy” (Commentary on Hebrews, 323).
So God is the One who is ultimately saving His people, but His method of saving them is through the means of convincing them to believe and hold onto the vitality of their faith in Christ and the gospel. Without His convincing us through His Word, and specifically here, the warnings laid out for us, the ends would not be accomplished in the way that He has decreed them to be. It is through our choosing that God's choice is brought to fruition, not apart from it. It is, therefore, necessary for us to be alarmed by the warning passages, not knowing whether we will continue on in the faith or not, in order that we might continue on indeed.
Of course, those who reject, in all reality, never were saved, and the author indicates this by his switch of audience (third person for those who reject and second person for the Christians he is addressing); but he does this to use those who reject as a terrifying reminder that, from our perspective, one can strongly believe and then slowly drift or abruptly walk away.
The love of Christ, and the terror of being away from God in eternity, stirs the true believer to the decision to hold on tighter than before, and through his being stirred, God brings him to glory.
Therefore, let us fear lest, while a promise remains of entering His rest, any one of you should seem to have come short of it. For indeed we have had good news preached to us, just as they also; but the word they heard did not profit them, because it was not united by faith in those who heard. (Hebrews 4:1-2)