Hebrews 10:26-27 reads, "For if we sin willfully after we have received the knowledge of the truth, there no longer remains a sacrifice for sins, but a certain fearful expectation of judgment, and fiery indignation which will devour the adversaries." Some argue from this that willful or continual sin cannot be forgiven and salvation can be lost, or that those in view of judgment were never really saved to begin with. They would interpret the judgment as hell.
That those being warned are truly saved is very clear. Paul's use of "we" is more than rhetorical. He is warning readers who are Christians like himself (see "Interpreting Hebrews: Beginning with the Readers," GraceNotes no. 15) of something that is possible for Christians to do. The immediate context shows that this warning is for those who "have received the knowledge of the truth" (v. 26), are sanctified (v. 29), know God and are "His people" (v. 30), "were illuminated" and suffered for their faith (v. 32), and have "an enduring possession" in heaven (v. 34).
Since the Bible uniformly teaches that a person once saved cannot lose his or her salvation (see "Eternally Secure," GraceNotes no. 24), the loss of salvation cannot be in view here. Besides, most sins are intentional or willful to some degree. However, the Bible recognizes some sins that are unintentional (Num. 15:22-29). Perhaps neglecting to pray for someone would be an example of an unintentional sin. But in most cases the perpetrator knows that he or she is committing a sin.
Some interpret the willful sin as continual sin (NIV: "If we deliberately keep on sinning"), but this is reading too much into the present participle used for "to sin." The author of Hebrews apparently has a particular sin in mind, which becomes evident as we consult the context. He had exhorted his readers previously to hold fast to their confession (3:6; 4:14) and has warned them about the dangers of not pressing on in their faith (6:1-8; see "How Do We Explain Hebrews 6:4-8?" GraceNotes no. 39). He reinforces this concern in the verses just before this warning about the willful sin (10:23-25). The readers were on the verge of abandoning their confession of faith in Christ and returning to the Mosaic Law and its sacrifices, which is why he discussed the inadequacy of the Mosaic sacrifices especially from chapter 8 onward.
The willful sin would be a deliberate abandonment of their confession of the sufficiency of Christ's sacrifice for a return to insufficient Jewish sacrifices. The author had written them that "Christ was offered once to bear the sins of many" (9:28), that "by one offering He has perfected forever those who are being sanctified (10:14), and that once forgiven "there is no longer an offering for sin" (10:18). The Law offered them nothing since it looked forward to the ultimate sacrifice of Jesus Christ (10:1-10). Should they turn back to the Law, Christ's perfect and eternal sacrifice would be sufficient to cover even that great and willful sin soteriologically, but they would still face a severe non-soteriological judgment. The author had just referred to an approaching "Day" (v. 25) implying that there will be an accounting, which we know as the Judgment Seat of Christ taught in so many other places in the New Testament (e.g., Rom. 14:10-12; 1 Cor. 3:11-15; 2 Cor. 5:10).
The background for understanding this passage is very likely Numbers 15:30-31. There we see that for certain serious (or presumptuous) sins no sacrifices were stipulated, therefore those who committed those sins were "cut off" from their people (put to death). The author is saying that if the readers of Hebrews abandon the only sufficient sacrifice for their sins, they too will be judged severely.
Because the author uses strong language ("fearful expectation of judgment and fiery indignation") and speaks of a punishment worse than death (v. 30), many conclude he is threatening them with eternal hell fire. But because they are Christians who cannot lose their salvation and because he has in view the Judgment Seat of Christ, this cannot be. The exact judgment is not specified, only its severity. It is hard to imagine a judgment worse than death, but human experience does testify that there are occasions when death is more enticing than severe suffering (Just ask Jonah! Jonah 4:3). The author is comparing this judgment to the death penalty for the presumptuous sin of Numbers 15:30-31, which was the severest penalty dictated at that time. But in light of New Testament revelation about the Judgment Seat of Christ, we know that a more severe judgment would be a negative assessment there because of the eternal implications.
The possibility of a negative assessment at the Judgment Seat of Christ is a "fearful expectation of judgment" (cf. 2 Cor. 5:9-11) for those who have not done good. The "fiery indignation which will devour the adversaries" (literally "fiery zeal") refers to the zeal of God's judgment toward sin. Believers can experience the same zeal of judgment toward their sin as God's enemies experience toward theirs, though the results are different. In the end, these readers who would be judged are still "His people" (v. 30; a quote from Deut. 32:35-36). They will not fall into hell, but "into the hands of the living God" (v. 31). Though at first glance fire may conjure up thoughts of hell, fire was actually used often in the Old Testament to judge or threaten judgment on God's own people (see "Hebrews on Fire," GraceNotes no. 34).
Jesus Christ died for all sins, even willful sins, but if the readers of Hebrews turn back to Mosaic sacrifices, they will not find there any greater provision for forgiveness and they will face a severe judgment at the Judgment Seat of Christ. There is no other refuge from sin's penalty than the sacrificial blood of Jesus Christ. This should be a warning to us also to look only to Jesus Christ for forgiveness because of His fully efficacious death and resurrection. "For by one offering He has perfected forever those who are being sanctified" (10:14).