Exodus 20:19

And they said unto Moses, Speak thou with us, and we will hear: but let not God speak with us, lest we die.

And they said unto Moses, Speak thou with us ... but let not God speak with us. It was the heads of the people and the elders who came (see their application to Moses fully detailed, Deuteronomy 5:22), while they perceived in the phenomena on the mount the ensigns of His presence. They had heard Him proclaim the moral law with an articulate voice, and that voice was more appalling to them than the loudest peals of thunder. Mankind are weak creatures at the best; and all the uncommon appearances or extraordinary occurrences of nature are to them messengers of terror, for they are associated with ideas of danger. Men are also guilty creatures; and every indication of supernatural power makes their hearts tremble with alarm, lest the power should be exerted for their punishment. It is not wonderful, then, that the Israelites were struck with consternation at the scenes of which they had been eye-witnesses and ear-witnesses. But they were more afraid at the voice of Yahweh than all the rest, and entreated that He Himself would not speak to them anymore. Even Moses himself was overpowered with fear (Hebrews 12:21).

This request made to Moses was an evidence that the grand design of the appalling phenomena on the mount-namely, that of convincing everyone of sin, and showing them the necessity of a Mediator-had been accomplished. For they, who at first could scarcely be restrained from bursting through the barriers that prevented their access to the hill, became afterward so overwhemed with terror that they shrunk back from their station, and begged that God would no longer deliver his commands to them in that way, 'lest they should die.' They desired that Moses might act as a mediator between God and them, and that all future revelations of the divine will might be made to them through his agency. They were probably not aware of the full import of their request, and how much they stood in need of a greater Mediator than he. But God granted their petition, by not only appointing Moses to negotiate with Him in their stead, but promising that, at a future period, another Mediator of still higher character and qualifications should appear. For it was at this time, as we learn from Deuteronomy 18:15, that the promise of the great Prophet was made to them.