Exodus 19:18
16 On the third day in the morning there was thunder and lightning and a dense cloud on the mountain, and the sound of a very loud horn; all the people who were in the camp trembled. 17 Moses brought the people out of the camp to meet God, and they took their place at the foot of the mountain. 18 Now Mount Sinai was completely covered with smoke because the Lord had descended on it in fire, and its smoke went up like the smoke of a great furnace, and the whole mountain shook violently. 19 When the sound of the horn grew louder and louder, Moses was speaking and God was answering him with a voice. 20 The Lord came down on Mount Sinai, on the top of the mountain, and the Lord summoned Moses to the top of the mountain, and Moses went up.
Hebrews 12:18
16 And see to it that no one becomes an immoral or godless person like Esau, who sold his own birthright for a single meal. 17 For you know that later when he wanted to inherit the blessing, he was rejected, for he found no opportunity for repentance, although he sought the blessing with tears. 18 For you have not come to something that can be touched, to a burning fire and darkness and gloom and a whirlwind 19 and the blast of a trumpet and a voice uttering words such that those who heard begged to hear no more. 20 For they could not bear what was commanded: “If even an animal touches the mountain, it must be stoned.”
Notes and References
"... In Galatians, Paul develops an allegory of Sinai and the Jerusalem above, with Sinai representing the old covenant, slavery and the “present Jerusalem,” in contrast with the freedom of the “Jerusalem above” (Galatians 4:21–31). We also note the use of Sinai imagery in Hebrews 12:18–29, where that mountain comes to represent the old covenant while Mt. Zion represents the new covenant that takes its place ..."
Ryken, Leland Dictionary of Biblical Imagery (p. 2671) InterVarsity Press, 1998