What did "v'Higbalta Es ha'Har" entail?
Rashi and Rashbam: Moshe had to actually place markers along the borders of Har Sinai, and to warn Yisrael not to cross them.
What are the connotations of "Leimor"?
Rashi: It means that the markers would 'tell them' not to go past them. 1
Otherwise, it would have been more appropriate to write 'v'Amarta Aleihem.' Also see Sifsei Chachamim citing Mizrachi, and see Gur Aryeh below.
Why were the people forbidden to ascend the mountain?
Oznayim la'Torah: Because Moshe was having a private audience with Hashem, nobody was allowed to be present 1 (even though they were permitted to listen).
Oznayim la'Torah: It is similar to the Kohen Gadol on Yom Kipur, about which the Torah writes, "v'Chol Adam Lo Yih'yeh b'Ohel Mo'ed ..." (Vayikra 16:17). See Oznayim la'Torah who elaborates.
Why was a seemingly-minor infraction (passing the boundary) punishable by death?
Seforno: To serve as a deterrent - to prevent the people, who were already keen to come closer, from breaking through and seeing more, in which case many of them would die and Hashem's Simchah would be disturbed, when their corpses rendered the location impure and when their relatives would mourn their death, with the result that the Shechinah would not rest with them.
How would someone who transgresses die?
Moshav Zekenim: He would be stoned bi'Yedei Shamayim 1 - despite that the Shechinah is there, like Nadav and Avihu died in the Mishkan. 2
Rashbam: The people should kill him (refer to 19:13:1:1).
Targum Yonasan: Refer to 19:13:1:2 .
QUESTIONS ON RASHI
Rashi writes: "Leimor - The boundary [itself] would say to them, 'Take heed, lest you ascend from this point onwards!" Why not explain simply, that Moshe should say this to them?
Gur Aryeh: If so, it should have sufficed to say, 'Bound in the nation... and they should take heed lest they ascend, etc." - leaving it self-explanatory that Moshe should say this to the nation. The word "Leimor" is extra, as is the direct warning "Hishameru Lachem" (you take heed). This teaches that the boundary itself should give them this warning. 1
It would be insufficient to warn Yisrael verbally; rather Moshe had to demarcate a tangible boundary, which would indicate to them that it was forbidden to pass. Also see Mizrachi.
Rashi writes: "The boundary [itself] would say to them ... and you [Moshe] should warn them about this." How do we derive that Moshe should tell them as well?
Gur Aryeh: Otherwise, why did Hashem need to inform Moshe what the boundary would say? 1 It must be, so that Moshe would infer a Kal va'Chomer, that he too must warn Bnei Yisrael about this.
Hashem needed to tell Moshe only to make the boundary; but as for what the boundary would say - let the Bnei Yisrael hear for themselves!
Rashi writes: "[Take heed lest you] touch its edge - [i.e.] even its edge." Why explain this way?
Gur Aryeh: It would not make any sense to say that only the very edge of the border was forbidden, but to leap over the border and land inside it would be permitted!
