What does Hebrews 10:30 mean?

This verse is part of a passage which generates controversy. Read out of context, it can be misinterpreted to suggest that those who are saved, but sin, are at risk of being damned. The writer of Hebrews continues to use language in this passage which indicates he is speaking of a truly saved believer (Hebrews 10:29). However, the context of the New Testament does not support the idea that a saved Christian can lose that salvation (John 10:28–29), so the judgment being spoken of here must not be a reference to eternal judgment.

That being said, even in context, the exact meaning of these words can be difficult to untangle. One popular view is that this is an alert given to those who are "almost" saved—persons who have a clear understanding of the gospel, but reject it anyway. The more likely subject, given the whole context of the passage, is a warning to Christians in the same vein as the one given in chapter 3. Namely, that there will be consequences for disobedience, even for God's chosen people, even for God's saved believers. The prior verse pointed out that those who have the most knowledge of the truth—in this case, Christians—deserve all the more punishment for violating that truth.

To support this idea, the writer quotes from Deuteronomy 32:35–36, which is part of the song of Moses. That verse refers to God taking "vengeance" on the enemies of Israel for their aggression against His people. However, the context of that aggression, according to Deuteronomy, is the sin of Israel herself! So, while the quote specifically targets the enemies of Israel, it comes from a passage describing God's punishment of His own disobedient children.