Matthew Poole and continuators on Hebrews 12:20

20 For they could not endure that which was commanded. And if so much as a beast touch the mountain, it shall be stoned, or thrust through with a dart.

The reason of the foregoing Deprecation, and which adds to the Terribleness of this Covenant-Dispensation; for the Voice surpassed their Strength and Capacity, that they must die, if they heard it any more; so dreadful was the sound and matter of it: for the Commandment and threatning was, That if any Man or Beast did but as much as touch the Mountain, they should die for it, Exod. 19.12, 13, 21, 23, 24. Therefore was Moses so strictly charged to look to it, and to provide against it, shewing the Dreadfulness of that Covenant-Dispensation, that if Men did not keep their Beasts from coming near, they should be stoned, or darted to Death; how much more themselves, if they should transgress the Law, which, tho it was designed to lead them unto Christ, yet was not generally so discerned or used by them. So that if the Publication of it be so terrible, how much more the Punishment for breaking it? Exod. 20.20.