Exodus 19:16-20

16 On the morning of the third day there were thunders and lightnings and a thick cloud on the mountain and a very loud trumpet blast, so that all the people in the camp trembled. 17 Then Moses brought the people out of the camp to meet God, and they took their stand at the foot of the mountain. 18 Now Mount Sinai was wrapped in smoke because the Lord had descended on it in fire. The smoke of it went up like the smoke of a kiln, and the whole mountain trembled greatly. 19 And as the sound of the trumpet grew louder and louder, Moses spoke, and God answered him in thunder. 20 The Lord came down on Mount Sinai, to the top of the mountain. And the Lord called Moses to the top of the mountain, and Moses went up.

It's a tremendous scene—thunder and lightning and smoke, but to his credit, Moses is not afraid.

This reminds me of the scene in the gospels on the Mount of Transfiguration, when Peter, James, and John are with Jesus when something miraculous occurs:

17 And after six days Jesus took with him Peter and James, and John his brother, and led them up a high mountain by themselves. 2 And he was transfigured before them, and his face shone like the sun, and his clothes became white as light. 3 And behold, there appeared to them Moses and Elijah, talking with him. 4 And Peter said to Jesus, “Lord, it is good that we are here. If you wish, I will make three tents here, one for you and one for Moses and one for Elijah.” 5 He was still speaking when, behold, a bright cloud overshadowed them, and a voice from the cloud said, “This is my beloved Son, with whom I am well pleased; listen to him.” 6 When the disciples heard this, they fell on their faces and were terrified. 7 But Jesus came and touched them, saying, “Rise, and have no fear.” 8 And when they lifted up their eyes, they saw no one but Jesus only. [Matthew 17:1-8]

The same Lord who was at Sinai with Moses is there present on the Mount of Transfiguration, and the experience is dazzling. No wonder the people trembled and the disciples were terrified!