Dr. Robert Gagnon (author of the must-read The Bible and Homosexuality: Texts and Hermeneutics) posted the following on his wall (it was a public post). I thought readers of this blog will appreciate this:
The Letter to the Hebrews is the easiest book in the Bible to demonstrate that salvation can be lost or forfeited, though such a view is present throughout the NT in nearly every NT book (1-chapter letters excluded). Showing from Hebrews that it is possible for genuine believers who swerve from the faith to fall away is like shooting fish in a barrel. It's too easy. Indeed, the writer of Hebrews is a step beyond other New Testament writers in thinking not only that believers can fall away from the faith but also that it is impossible for those who do so to return to the faith at a later time.
"For it is impossible to renew again to repentance those who once were enlightened [or: illuminated, brought into the light] and tasted of the heavenly gift and became partakers of the Holy Spirit and tasted the good word of God and the powers of the age to come and (then) fell away since they are re-crucifying for themselves the Son of God and making a public example of him [or: are exposing him to public disgrace, i.e., referring to the ignominy of crucifixion]." (Heb 6:4-6; GET)
There is little chance that faux Christians are in view here. The language of “renewing again to repentance” can have in view only once-genuine Christians. The reference to “falling away” means what it says. The “heavenly gift” of “partaking of the Holy Spirit” is available only to believers. Mention of “re-crucifying” the Son of God can refer only to an attempt to receive the benefits of the atonement a second time. Also confirming that Paul has in view genuine believers who have fallen away is the remark in 6:10 that “God is not unjust to forget [or: overlook] your work and the love that you demonstrated for his name in having served [or: ministered to, helped] the saints and (still) serving (them).”
Some attempt to undermine this obvious conclusion by citing the writer’s remark in 6:9 (“We are confident concerning you, beloved, of better things and of things being held firmly for salvation, even though we speak in this way”) as possibly showing that 6:4-6 has in view persons who “were not truly regenerate.” However, the description given both in 6:4-6 and in 6:9-10 demonstrates conclusively that the persons in question were truly regenerate. The writer’s point is simply that he has good reason to be hopeful that in the particular case of the believers to whom he is writing (probably in Italy, 13:24) there will be no falling away from the faith.
There are, of course, other passages in Hebrews that continue this theme:
"For (if) we (keep on) sinning willfully [or: deliberately, intentionally] after receiving the knowledge of the truth, there is no longer left a sacrifice for sins but a fearful prospect [or: expectation] of judgment and a raging fire [literally: a zeal of fire] that is about to consume the adversaries. Anyone who set aside the law of Moses 'dies' without mercy 'on (the testimony of) two or three witnesses' [Deut 17:6]. How much worse punishment [or: vengeance, retribution] do you think will be deserved by the one who trampled under foot the Son of God and regarded as unholy [or: profane; literally: common, ordinary] the blood of the covenant by which he was made holy [or: sanctified] and insulted the Spirit of grace? For we know the one who said, 'Avenging belongs to me, I will pay back' [Deut 32:35], and again, 'The Lord will judge his people' [Ps 135:14]. It is a fearful thing to fall into the hands of the living God. (Heb 10:26-31; GET)
The message is very clear: Any who reject what Jesus has done for them on the cross, either explicitly through outright renunciation or implicitly through a life under sin’s primary control, will face fearful, cataclysmic judgment at the hands of God. Rather than conclude that the grace of God in Christ means exemption from penalties, the author of Hebrews uses a lesser-to-the-greater argument: If violating the law of Moses with impunity invited instant death, it will be far worse for those who reject Christ’s holy work because the latter is greater than the law of Moses.
While urging his readers in 12:15-29 not to refuse God who is speaking, the author of Hebrews cites the example of Esau for whom it was too late to repent after he gave up his birthright, warning his readers that they have no guarantee that God will take them back if they fall away from the faith and then want to return. He reminds his readers that the terrifying theophany at the giving of the law at Sinai will be nothing compared to the time just preceding the recreation of the world. There is a greater certainty of punishment for those who ignore the warnings of the God who shakes all at the End.
"Pursue … the holiness without which no one will see the Lord, taking care that … no one is sexually immoral or profane [or: impure, worldly, irreverent, unholy] like Esau who (in exchange) for one meal sold his own birthright (as firstborn). For you know [or: For know] that also afterwards, when he wanted to inherit the blessing, he was rejected as unfit, for he found no place [or: opportunity, occasion, chance] for repentance, though he sought it out with tears…. See that you do not refuse the one who is speaking. For if those people did not escape when they refused the one warning on earth, much more we who are turning away from the one (warning) from heaven, whose voice at that time shook the earth but now he has promised, saying, 'Once more I will shake' not only 'the earth' but also 'the heaven [Hag 2:6, 21].'" (Heb 12:14, 16-17, 25-26; GET)
According to 3:7-4:13, the fact that the wilderness generation that left Egypt under Moses perished without entering into God’s “rest” (cf. Ps 95:7-11) because of their unbelief, means that the same fate could befall followers of Christ if they harden their hearts to God’s voice in Christ:
"See (to it), brothers (and sisters), that there will never be among any of you an evil heart of unbelief in standing aloof [or: departs, withdraws, shrinks, keeps far, falling away, turning away, revolting] from the living God. But exhort yourselves each and every day … in order that none of you may be hardened by the deceitfulness of sin—for we have become partakers of Christ if we hold firm to the original commitment [or: undertaking, resolution, confidence, foundation, substance, reality] until the end…. And we see that they (i.e. the wilderness generation of Israel) that they were not able to enter (God’s resting place for them in the promised land) because of unbelief." (Heb 3:12-14, 19; GET)
The author also contends that no previous generation had attained God’s “sabbath rest,” that this rest is still future for the people of God. He then exhorts those who are Christ’s: “Let us make every effort to enter into that rest in order that no one may fall by the same example [or: pattern] of disobedience” that one sees in the wilderness generation of Israelites (4:8-11).
According to 2:1-4, if Jesus is superior to angels, then the penalty for neglecting the salvation available in Christ must be greater than the penalty for transgressing the law of Moses declared through angels. One might expect the author to talk about greater grace; instead he stresses that rejection of Christ means a greater rejection and a greater offense against God.
The evidence from Hebrews that even genuine Christians could depart from the faith and be excluded from God's kingdom is thus overwhelming.
The denial even of "second repentance" is distinctive to Hebrews, an outlier position within the canon. There may be more than one position on this issue in Scripture, or the position reflected in Hebrews may apply to those who, as part of a community, emphatically and irrevocably renounce Christ.
[Reposted with slight alterations from July 2021]