Contradiction with Exodus 19:12
This verse instructs that no one should touch the mountain, directly leading to the death penalty, which contradicts the suggestion in Hebrews 12:20 of an imposed prohibition without the explicit command of death for touching the mountain.
Exodus 19:12: And thou shalt set bounds unto the people round about, saying, Take heed to yourselves, [that ye] go [not] up into the mount, or touch the border of it: whosoever toucheth the mount shall be surely put to death: