Exodus 19:23

Moses said to the Lord, “The people cannot come up to Mount Sinai, because You warned us, saying, ‘Set barriers around the mountain and consecrate it.’”

Exodus 19:12

You shall set barriers for the people all around [the mountain], saying, ‘Beware that you do not go up on the mountain or touch its border; whoever touches the mountain must be put to death.

Joshua 3:4-5

However, there shall be a distance between you and it of about 2,000 cubits (3,000 ft.) by measurement. Do not come near it, so that you may [be able to see the ark and] know the way you are to go, for you have not passed this way before.”

Treasury of Scripture Knowledge

Summary

And Moses said unto the LORD, The people cannot come up to mount Sinai: for thou chargedst us, saying, Set bounds about the mount, and sanctify it.

Bible References

Set bounds

Exodus 19:12
You shall set barriers for the people all around [the mountain], saying, ‘Beware that you do not go up on the mountain or touch its border; whoever touches the mountain must be put to death.
Joshua 3:4
However, there shall be a distance between you and it of about 2,000 cubits (3,000 ft.) by measurement. Do not come near it, so that you may [be able to see the ark and] know the way you are to go, for you have not passed this way before.”