Hebrews 12:25-26

25See to it that you do not refuse him who speaks. If they did not escape when they refused him who warned them on earth, how much less will we, if we turn away from him who warns us from heaven? 26At that time his voice shook the earth, but now he has promised, “Once more I will shake not only the earth but also the heavens.” Haggai 2:6