Exodus 19:23

And Moses saith unto Jehovah, 'The people is unable to come up unto mount Sinai, for Thou -- Thou hast protested to us, saying, Make a border for the mount, then thou hast sanctified it.'

Exodus 19:12

And thou hast made a border for the people round about, saying, Take heed to yourselves, going up into the mount, or coming against its extremity; whoever is coming against the mount is certainly put to death;

Joshua 3:4-5

only, a distance is between you and it, about two thousand cubits by measure; ye do not come near unto it, so that ye know the way in which ye go, for ye have not passed over in the 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 hast made a border for the people round about, saying, Take heed to yourselves, going up into the mount, or coming against its extremity; whoever is coming against the mount is certainly put to death;
Joshua 3:4
only, a distance is between you and it, about two thousand cubits by measure; ye do not come near unto it, so that ye know the way in which ye go, for ye have not passed over in the way heretofore.'