John Calvin Commentary Hebrews 12:19

"and the sound of a trumpet, and the voice of words; which [voice] they that heard entreated that no word more should be spoken unto them;" — Hebrews 12:19 (ASV)

Those who heard entreated, etc. This is the second clause, in which he shows that the Law was very different from the Gospel. For when it was promulgated, there was nothing but terrors on every side. For everything we read of in Exodus 19 was of this kind, and intended to show the people that God had ascended his tribunal and manifested himself as a strict judge. If by chance an innocent beast approached, he commanded it to be killed: how much heavier punishment awaited sinners who were conscious of their guilt, indeed, who knew themselves to be condemned to eternal death by the Law? But the Gospel contains nothing but love, provided it is received by faith. What remains to be said you can read in 2 Corinthians 3.

But by the words the people entreated, etc., it should not be understood that they refused to hear God, but that they prayed not to be constrained to hear God himself speaking; for by the interposition of Moses their dread was somewhat mitigated. Yet interpreters are at a loss to know why the Apostle ascribes these words to Moses, I exceedingly fear and quake; for we read nowhere that they were expressed by Moses. But the difficulty may be easily removed, if we consider that Moses spoke in this manner in the name of the people, whose requests as their delegate he brought to God. It was, then, the common complaint of the whole people; but Moses is included, who was, as it were, the speaker for them all.