Hebrews 12:25 See that you do not refuse Him who speaks. For if they did not escape who refused Him who spoke on earth, much more shall we not escape if we turn away from Him who speaks from heaven, [26] whose voice then shook the earth; but now He has promised, saying, “Yet once more I shake not only the earth but also heaven.”
The contrast is made again with the Sinaitic covenant between God and the Jews, and the Heavenly, eternal covenant made in Christ. The author has been exploiting this imagery since verse 18 to help his Jewish readership ascertain the benefit of knowing Jesus as Lord, and relying solely on Him for one’s eternal destiny.