The following is an excerpt from The MacArthur New Testament Commentary on Hebrews 6.

For 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, and have tasted the good word of God and the powers of the age to come, and 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. (6:4–6)Still speaking to the unsaved who have heard the truth and acknowledged it, but who have hesitated to embrace Christ, the Holy Spirit gives a fourth warning, the crux of 6:1–8. Summarized, the warning is: “You had better come to Christ now, for if you fall away it will be impossible for you to come again to the point of repentance.” They were at the best point for repentance—full knowledge. To fall back from that would be fatal.

Because they believe the warning is addressed to Christians, many interpreters hold that the passage teaches that salvation can be lost. If this interpretation were true, however, the passage would also teach that, once lost, salvation could never be regained. If, after being saved, a person lost his salvation, he would be damned forever. There would be no going back and forth, in and out of grace. But Christians are not being addressed, and it is the opportunity for receiving salvation, not salvation itself, that can be lost.

The believer need never fear he will lose his salvation. He cannot. The Bible is absolutely clear about that. Jesus said, “My sheep hear My voice, and I know them, and they follow Me; and I give eternal life to them, and they shall never perish; and no one shall snatch them out of My hand. My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of the Father’s hand” (John 10:27–29). Paul is equally clear. “Who shall separate us from the love of Christ? Shall tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword? … For I am convinced that neither death, nor life, nor angels, nor principalities, nor things present, nor things to come, nor powers, nor height, nor depth, nor any other created thing, shall be able to separate us from the love of God, which is in Christ Jesus our Lord” (Rom. 8:35, 38–39). “He who began a good work in you will perfect it until the day of Christ Jesus” (Phil. 1:6). We are “to obtain an inheritance which is imperishable and undefiled and will not fade away, reserved in heaven,” and we “are protected by the power of God through faith for a salvation ready to be revealed in the last time” (1 Pet. 1:4–5). If the power of God cannot keep us, nothing is dependable or trustworthy or worth believing in. A Christian has no reason at any point in his life to believe that his salvation is or can be lost. If by Christ’s death we can be saved, certainly by His life of power and intercession we can be kept saved (Rom. 5:10).

It is unbelievers who are in danger of losing salvation—in the sense of losing the opportunity ever to receive it. The unbelieving Jews were in great danger, because of their spiritual immaturity and sluggishness, of turning back to Judaism and of never being able to repent and come to Christ. They would be lost forever, because they had rejected, at the most vital point in knowledge and conviction, the only gospel that could save them. There is no other salvation message they could hear, no evidence of the truth of the gospel they had not seen.

These particular Jews had even heard the apostles preach and had seen them perform signs and wonders and miracles (Heb. 2:4). They had been privileged to behold virtually all the manifestations of His saving Word and power that God could give. They had heard it all and seen it all. They even had accepted it all intellectually. Any who are so informed, so witnessed to, so blessed with every opportunity to know God’s gospel, and who then turn their backs on it—for Judaism or anything else—are eternally lost. They not only reject the gospel, but crucify to themselves the Son of God, and put Him to open shame. They had either to go on to full knowledge of God through faith in Christ or else turn away from Him, to become apostate and be lost forever. There was no other alternative.

Some have translated adunatos (impossible) in 6:6 as “difficult.” But it is clear even from other passages in Hebrews that such a translation is unjustified. The same Greek word is used in 6:18 (“It is impossible for God to lie”), in 10:4 (“It is impossible for the blood of bulls and goats to take away sins”), and in 11:6 (“Without faith it is impossible to please Him”). All three of these passages would be nonsense if “impossible” were changed to “difficult.” The harsh finality of the danger cannot be escaped or minimized.

A vaccination immunizes by giving a very mild case of the disease. A person who is exposed to the gospel can get just enough of it to immunize him against the real thing. The longer he continues to resist it, whether graciously or violently, the more he becomes immune to it. His spiritual system becomes more and more unresponsive and insensitive. His only hope is to reject what he is holding onto and receive Christ without delay—lest he become so hard, often without knowing it, that his opportunity is forever gone.

To renew means to restore, to bring back to an original condition. The original condition of these Jews was that of excitement about the gospel when they first heard it. It was beautiful. They had moved from Judaism right up to the edge of Christianity, evidently even to repentance. They had turned from their old ways. They had tried to turn from their sin. They had begun to turn toward God. They had come all the way up to the edge of salvation. All the revelation God had He had given them. There was nothing else He could say or do. If they fell away they did so with an evil heart of unbelief and they did it against full revelation. They had the advantage of having been raised under the Old Covenant and they had heard and seen all the beauty and perfection of the New. If they now fell away from that, if they now departed from the living God, there was no hope that they could ever be restored to the place where the gospel was fresh, where the gospel taste was sweet, where repentance was a proper response. They could never get back there. When one rejects Christ at the peak experience of knowledge and conviction, he will not accept at a lesser level. So salvation becomes impossible.

They could not return because they had crucified to themselves the Son of God, and put Him to open shame. To themselves simply means that, as far as they were concerned, the Son of God deserved to be crucified. Regardless of what they may still have been professing openly and publicly, they now took their stand with the crucifiers. In their hearts they said, “That’s the same verdict we give.” They had made trial of Jesus Christ and, with all the evidence possible, they decided He was not the true Messiah. They had turned around and gone back to Judaism. To them Jesus was an impostor and deceiver and got exactly what was coming to Him. They agreed with those who killed Jesus, and they put Him to an open shame again. Shame here connotes guilt. They declared openly that Jesus was guilty as charged.

When anyone has heard the gospel and then turns away, he has done exactly what these Jews did. Though he would never take up a hammer and spikes and physically nail Jesus to a cross, he nevertheless agrees to Jesus’ crucifixion. He takes his place with the crucifiers. If this happens with full light, such a person has become an apostate, and for him salvation is forever out of reach. He has rejected Jesus Christ against the full light and power of the gospel. He is incurably anti-God, and for him is reserved the hottest hell. He takes his place with Judas, who walked and talked and ate and fellowshipped with God incarnate, yet finally rejected Him. “How 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?” (Heb. 10:29).

It is dangerously self-deceptive for a person to think that, by staying on the sidelines, by holding off deciding, by thinking himself tolerant of the gospel simply because he does not outwardly oppose it, that he is safe. The longer one stays on the edge the more he leans toward the old life. Staying there too long inevitably results in falling away from the gospel forever. It may not be, and often is not, a conscious decision against Christ. But it is a decision and it is against Christ. When a person goes away from Him in full light, he places Him on the cross again, in his own heart, and puts himself forever out of the Lord’s reach.

How terribly serious it is to reject Jesus Christ.John MacArthur, Hebrews (Chicago: Moody Press, 1996), 146-49.