Commentators explain this verse is a powerful combination of prophecies from Isaiah 26:20 and Habakkuk 2:3. The author of Hebrews intentionally adapts the text to show that the Old Testament's promised deliverance is fulfilled in a person: Jesus Christ. This isn't just a hopeful sentiment; it's a direct, authoritative promise from God that 'He who is coming' will certainly arrive, giving believers a firm foundation for their endurance.