Exodus 19:21
"And the LORD said unto Moses, Go down, charge the people, lest they break through unto the LORD to gaze, and many of them perish."
Cross References (ranked by relevance)
And he smote the men of Bethshemesh, because they had looked into the ark of the LORD, even he smote of the people fifty thousand and threescore and ten men: and the people lamented, because the LORD had smitten many of the people with a great slaughter.
And he said, Draw not nigh hither: put off thy shoes from off thy feet, for the place whereon thou standest is holy ground.
Keep thy foot when thou goest to the house of God, and be more ready to hear, than to give the sacrifice of fools: for they consider not that they do evil.
And he said, Thou canst not see my face: for there shall no man see me, and live.
And Moses said, I will now turn aside, and see this great sight, why the bush is not burnt.