Charles Ellicott Commentary Exodus 20:18-21

"And all the people perceived the thunderings, and the lightnings, and the voice of the trumpet, and the mountain smoking: and when the people saw it, they trembled, and stood afar off. And they said unto Moses, Speak thou with us, and we will hear; but let not God speak with us, lest we die. And Moses said unto the people, Fear not: for God is come to prove you, and that his fear may be before you, that ye sin not. And the people stood afar off, and Moses drew near unto the thick darkness where God was." — Exodus 20:18-21 (ASV)

AT THE PEOPLE’S REQUEST, MOSES BECOMES THEIR INTERMEDIARY.

The delivery of the Ten Commandments by a voice manifestly superhuman impressed the people with profound fear. They felt the near contact with God to be more than they could bear. Even Moses was so deeply moved that he exclaimed, “I exceedingly fear and quake” (Hebrews 12:21). The people were still more afraid, and felt compelled to withdraw to a distance, beyond the sound of the terrible voice. From Deuteronomy we learn that they retired within their tents (Deuteronomy 5:30), having first sent a deputation to Moses, with a request that he would from then on act as their intermediary. It pleased God to assent to this proposal; and the remainder of the Law was communicated by God to Moses, and by Moses to the Israelites.