The warning to those who continue to sin wilfully, even after they know the truth of the gospel
Now let's examine a very grim passage. It clearly seems to be speaking about those who have been real believers but have ended up turning away from their faith. The Bible uses very stark language. It says they have "trampled under foot the Son of God".
26For if we go on sinning willfully after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27but a terrifying expectation of judgment and the fury of a fire which will consume the adversaries. 28Anyone who has set aside the Law of Moses dies without mercy on the testimony of two or three witnesses. 29How much severer punishment do you think he will deserve who has trampled under foot the Son of God, and has regarded as unclean the blood of the covenant by which he was sanctified, and has insulted the Spirit of grace? 30For we know Him who said, "vengeance is mine, I will repay" And again, "the Lord will judge his people."31It is a terrifying thing to fall into the hands of the living God.
Hebrews 10:26-31 (NASB)
The passage above can presumably only be referring to Christians who have been real, at least for a time. It refers to them "receiving the knowledge of the truth" and, even more importantly, to them having been "sanctified". Sanctification can only occur in the life of a real Christian, not an unbeliever. Yet, the direct warning is given, even to such people, that they must not go on sinning wilfully after receiving the knowledge of the truth (i.e. after becoming a Christian).
Note how strong the warning is. It specifically warns of how much more severe the punishment will be for such people, i.e. as compared to how it will be for unbelievers who were never Christians in the first place. That has to mean that the writer of the letter to the Hebrews is saying, as the apostle Paul also said above, that a real believer who falls away is in a substantially worse position than someone who has never believed at all.
Logically, that must mean that a real believer who falls away will go, in the end, to the Great White Throne judgment for unbelievers and from there to the Lake of Fire. What else can we possibly conclude? If it did not mean that, then how can it be said that such a person will be treated more severely than one who never knew the truth? We know for a fact that unbelievers are going to the Lake of Fire.
That means that for an apostate believer, (i.e. one who falls away and is unfaithful to Jesus), that somehow, whatever they experience in the Lake of Fire will be more intense than it will be for someone who had never believed. There are, evidently, degrees of punishment, even within the same Lake of Fire.
I don't know how that makes you feel, but it alarms me and increases my fear of the Lord. It makes me want to focus on God and on bearing fruit. I do not want to be classified as a worthless or unproductive servant, especially, given that it has such awesome significance in terms of how we will be judged.
People who fall away after knowing the truth find it very hard ever to repent again
If the previous passage was not enough to make you sit up and think, then consider this one. It indicates that a person who believes and then falls away will also find it very difficult to repent again later. Thus, if we do fall away, it will not be easy to find our way back:
4For in the case of those who have once been enlightened and have tasted of the heavenly gift and have been made partakers of the Holy Spirit, 5and have tasted the good word of God and the powers of the age to come,6and then have fallen away, it is impossible to renew them again to repentance, since they again crucify to themselves the Son of God and put Him to open shame. 7For ground that drinks the rain which often falls on it and brings forth vegetation useful to those for whose sake it is also tilled, receives a blessing from God;8but if it yields thorns and thistles, it is worthless and close to being cursed, and it ends up being burned.
This passage is clearly speaking of real Christians, not those who have never really believed to begin with. It says they "have been made partakers of the Holy Spirit". How could that be the case if they were never real believers?
So, the additional warning given to us is that if we do ever fall away, then we cannot complacently assume that we can be restored by repenting again later. Subsequent repentance may prove to be impossible, or at least very difficult. Therefore, the moral of all this is that we need to persist, and not to throw away the faith that we have. We must endure whatever trials and difficulties we face and never give up the faith. Then we will be rewarded. But if we do give up our faith and fall away, then we face "destruction". Whatever you believe that means exactly, you will have to agree that it cannot be said to be something positive:
35Therefore, do not throw away your confidence, which has a great reward. 36For you have need of endurance, so that when you have done the will of God, you may receive what was promised. 37for yet in a very little while, He who is coming will come, and will not delay. 38but my righteous one shall live by faith; and if He shrinks back, my soul has no pleasure in him. 39But we are not of those who shrink back to destruction, but of those who have faith to the preserving of the soul. Hebrews 10:35-39 (NASB)
That same hardening of our heart and conscience that causes us to fall away also has the effect of making our hearts too leathery and insensitive ever to repent of doing so. We must take very careful note of that and let it affect how we live, so that we resolve to make sure never to fall away. Remember also that in this next passage, God is described as a consuming fire, and that is in a letter which is addressed to Christians, not to unbelievers:
25See to it that you do not refuse Him who is speaking For if those did not escape when they refused him who warned them on earth, much less will we escape who turn away from Him who warns from heaven. 26And His voice shook the earth then, but now He has promised, saying, "yet once more I will shake not only the earth, but also the heaven." 27This expression, "Yet once more," denotes the removing of those things which can be shaken, as of created things, so that those things which cannot be shaken may remain. 28Therefore, since we receive a kingdom which cannot be shaken, let us show gratitude, by which we may offer to God an acceptable service with reverence and awe; 29for our God is a consuming fire. Hebrews 12:25-29 (NASB)