Hebrews 12:20

For they could not endure that which was commanded - They could not sustain the awe produced by the fact that God uttered his commands himself. The meaning is not that the commands themselves were intolerable, but that the manner in which they were communicated inspired a terror which they could not bear. They feared that they should die; Exodus 20:19.

And if so much as a beast touch the mountain, it shall be stoned - Exodus 19:13. The prohibition was, that neither beast nor man should touch it on pain of death. The punishment was to be either by stoning, or being "shot through."

Or thrust through with a dart - Exodus 19:13. "Or shot through." This phrase, however, though it is found in the common editions of the New Testament, is wanting in all the more valuable manuscripts; in all the ancient versions; and it occurs in none of the Greek ecclesiastical writers, with one exception. It is omitted now by almost all editors of the New Testament. It is beyond all doubt an addition of later times, taken from the Septuagint of Exodus 19:13. Its omission does not injure the sense.

12:20 For they could not bear - The terror which seized them, when they heard those words proclaimed, If even a beast, &c. Exodus 19:12 , &c.