Charles Ellicott Commentary Hebrews 12:20

"for they could not endure that which was enjoined, If even a beast touch the mountain, it shall be stoned;" — Hebrews 12:20 (ASV)

There is no sufficient reason for enclosing this verse and the next in parentheses.

And if so much as.—Better, If even a beast touch the mountain, it shall be stoned (Exodus 19:12–13). The next clause, “or thrust through with a dart,” is absent from our best authorities and has accidentally found its way into the text from Exodus 19:13.