And you shall set bounds for the people is literally “And you [singular] will delimit the people,” while the Septuagint says “And you will delimit the mountain.” The word really means to “mark a boundary” (Good News Translation), but round about does not specify either the people or the mountain. “Mountain” is not in the text at all, but the context clarifies the intended meaning. Some translations have added “the mountain”: “Set limits for the people all around the mountain” (New American Bible). (Similar is New International Version.) Good News Translation expands even more: “Mark a boundary around the mountain that the people must not cross.”
Saying introduces what Moses is to say to the people. This is a quote within a quote. Since what follows is a warning, Durham changes saying to “warning.” Take heed, literally “you be on guard for yourselves,” is a command to the people. New International Version has “Be careful,” New Jewish Publication Society’s Tanakh has “Beware,” and Contemporary English Version has “Warn the people.” Good News Translation changes to indirect speech.
That you do not go up into the mountain is literally “to go up on [or, in] the mountain.” The negative is not explicit but is implied by the command to Take heed. New Jewish Publication Society’s Tanakh has “Beware of going up the mountain.” Good News Translation has “and tell them not to go up the mountain.” Another way to say this is “Forbid the people to go up the mountain.” However, in languages that must use direct speech, one may say, for example, “Be careful that you do not go up the mountain,” or even “I forbid you to go up….” Or touch the border of it is literally “and to touch on its edge.” New International Version has “or touch the foot of it,” and Revised English Bible has “or even to touch its base.” The manner of touching is not indicated, nor whether it is with the hand or the foot. This border was probably determined by Moses, who was told to mark the boundaries of the mountain. Good News Translation‘s “even get near it” is a possible model. Another one is “warn the people not to go up the mountain or even touch any part of it.”
Whoever touches the mountain is literally “any toucher on the mountain.” Good News Translation turns this into conditional clause: “If anyone sets foot on it.” Shall be put to death, literally “dying he shall be caused to die,” is an emphatic statement of the consequence of touching the mountain. New International Version has “shall surely be put to death,” and Durham has “will certainly be executed.” Other ways to express this are “must suffer death” or “people [or, they] must kill him.” The idea is that the mountain is taboo, in the sense that it is untouchable, because it is God’s mountain, where God dwells. Therefore anyone who touches the mountain also becomes taboo. Consequently they have to be killed so that they will not spread the taboo to anyone else. This was not so much a form of punishment as the unfortunate consequence of violating the holiness, or taboo, of the mountain. (The same form of the verb phrase is used repeatedly in 21.12-17 for capital punishment.)
Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .