26 For if we sin willfully after we have received the knowledge of the truth, there no longer remains a sacrifice for sins,
The most important principle of interpretation is the context, especially the argument of an entire book of the Bible. The argument of the book of Hebrews is that Jesus (the Antitype, or that which is against the type) is “greater than” or “better than” the types found in the Old Testament. Jesus was the reality, whereas the types of the Old Testament were merely shadows or illustrations of the reality. A type only illustrates the truth; it is not the truth.
The fourth warning passage of Hebrews is found in verses 26 to 39. The writer had been speaking to “brethren” (He 10:19) who belonged to the New Covenant. These believers were to practice Christianity under four principles found in verses 22–25, the immediate context. Nevertheless, some were not keeping those principles (He 10:25). The context of verses 26–29 is cast in the context of remaining true to what the readers already believed. In addition, the following context indicates that the argument was to genuine believers (He 10:32–39). At a point in the past these Christians had endured suffering for the cause of Christ. They needed to develop the character of “endurance” (He 10:36). These believers were positionally sanctified, which is justification (He 10:29).
The writer of Hebrews presented this argument to Christians, not non-Christians. The argument of “greater than” revolves around the contrast between the Old Covenant and the New Covenant. The Old systems were types of the New. Jesus is greater than the priests, even the Melchizedekian priesthood, angels, and the sacrificial system of the Old Testament.
The historical background and argument of the book relates to Jews who became believers but desired to go back to Old Testament sacrifices (He 2:1; 3:7,8; 6:4). This is the “sin willfully” of this verse. It was abandonment of their belief in the mutual exclusiveness of Christ’s sacrifice for them. They wanted to mix unfinished Old Testament sacrifices with the finished work of Christ. This was a sin of blending what is true with what is false. The readers of Hebrews did not fully understand the implications of what they were doing. They thought that they could combine both, but this was a serious error.
The word “for” shows that New Covenant believers were in view (He 10:19–25). Some Jewish converts were about to “forsake the assembling” of themselves with the church. He now gave the reasons for the previous exhortations to believers. The context is dealing with genuine believers, not professing Christians.
if we [including the human author of Hebrews]
The writer included himself in the warning here, using the word “we.” Since the author of Hebrews embraced himself with the word “we”, this passage refers to Christians. Thus, the willful sin is something committed after a conversion. This sin is a violation of God’s standard for sacrifice for sin. This act cuts one off from fellowship with the One who saves him.
It is a sin to blend what is true with what is false.
The threat in this verse is not loss of salvation but a warning about temporal judgment against those who blend the finished work of Christ with any other means of salvation. It is also a sin to minimize the work that Jesus did on the cross.