Hebrews 12:25-26

12:25 Take care not to refuse the one who is speaking! For if they did not escape when they refused the one who warned them on earth, how much less shall we, if we reject the one who warns from heaven? 12:26 Then his voice shook the earth, but now he has promised, “I will once more shake not only the earth but heaven too.” ¹ 

[12:26]  ¹ sn A quotation from Hag 2:6.