Exodus 19:16

19:16 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.

Exodus 19:18

19:18 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.

Deuteronomy 5:23-25

5:23 Then, when you heard the voice from the midst of the darkness while the mountain was ablaze, all your tribal leaders and elders approached me. 5:24 You said, “The Lord our God has shown us his great glory and we have heard him speak from the middle of the fire. It is now clear to us that God can speak to human beings and they can keep on living. 5:25 But now, why should we die, because this intense fire will consume us! If we keep hearing the voice of the Lord our God we will die!