Charles Ellicott Commentary Hebrews 10:27

"but a certain fearful expectation of judgment, and a fierceness of fire which shall devour the adversaries." — Hebrews 10:27 (ASV)

But a certain fearful looking for.—Better, But a fearful awaiting of judgment, and a jealousy of fire that shall devour the adversaries. For Christ’s “waiting” servants, the thought of “judgment” is lost in that of “salvation” (Hebrews 9:27–28); for these sinners, nothing is left but the awaiting of judgment.

The next words are a partial quotation, or an adaptation, of Isaiah 26:11: Let them see (and be ashamed) the zeal for the people; yea, fire shall devour Thine adversaries. (The Greek translation gives the second clause correctly, but not the former part of the sentence.)

In the prophetic imagery of the Old Testament, the destruction of the enemies of Jehovah is only the other aspect of His zeal or jealousy for His people.

This imagery was familiar to every Hebrew, and no words could show more powerfully than these that to forsake Christ for Judaism was (not to join, but) to abandon “the people of God.” For such apostates, there remains the zeal, the jealous wrath, of a devouring fire. (Malachi 4:0)