Exodus 19:23

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

Exodus 19:12

And thou shall set bounds to the people round about, saying, Take heed to yourselves, that ye not go up onto the mount, or touch the border of it. Whoever touches the mount shall be surely put to death;

Joshua 3:4-5

Yet there shall be a space between you and it, about two thousand cubits by measure. Do not come near to it, that ye may know the way by which ye must go, for ye have not passed this way heretofore.

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
And thou shall set bounds to the people round about, saying, Take heed to yourselves, that ye not go up onto the mount, or touch the border of it. Whoever touches the mount shall be surely put to death;
Joshua 3:4
Yet there shall be a space between you and it, about two thousand cubits by measure. Do not come near to it, that ye may know the way by which ye must go, for ye have not passed this way heretofore.