Exodus 19:23

And Moses said to Jehovah, The people cannot come up to mount Sinai; for thou hast testified to us, saying, Set bounds about the mountain, and hallow it.

Exodus 19:12

And set bounds round about the people, saying, Take heed to yourselves, not to go up unto the mountain nor touch the border of it: whatever toucheth the mountain shall certainly be put to death:

Joshua 3:4-5

yet there shall be a distance between you and it, about two thousand cubits by measure. Ye shall not come near 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 set bounds round about the people, saying, Take heed to yourselves, not to go up unto the mountain nor touch the border of it: whatever toucheth the mountain shall certainly be put to death:
Joshua 3:4
yet there shall be a distance between you and it, about two thousand cubits by measure. Ye shall not come near it, that ye may know the way by which ye must go; for ye have not passed this way heretofore.