Why did the people gaze after Moshe whenever he went from the camp to the Ohel Mo'ed?
Rashi #1: In praise of Moshe - they would exclaim 'How praiseworthy is the man who knows with certainty that the Shechinah will follow him into his tent!'
Rashi (in Kidushin 33b, citing MidrashTanchuma) and Targum Yonasan: They gazed at the thickness of his thighs and neck, and said 'This is all from the money that we donated for the Mishkan. 1
Targum Yonasan: It was Resha'im who stared after him with an Ayin ha'Ra. 2
Daf Al ha'Daf (33b): This opinion explains it negatively, since the Torah writes "Vanitzvu", and "Netzavim" always refers to Dasan and Aviram (Nedarim 64b). The two opinions are actually a Machlokes Amora'im. See Torah Temimah, citing the Yerushalmi Bikurim, 3:3, and also note 11.
Peirush Yonasan: In accusation. See answer #2.
Why did the people stand until Moshe entered the Ohel Mo'ed?
Moshav Zekenim: From here we learn that one must stand for a Zaken, Chacham and Av Beis Din 1 until he is out of sight.
Kidushin, 33b (based on this Pasuk): When a Nasi (the president of the Sanhedrin) passes, one must stand from the moment that he comes into sight 2 and remain standing until he is seated in his place. 3
Oznayim la'Torah: They rose in honor of Moshe, to atone for the lack of respect that they displayed when he failed to return - from Har Sinai - at the time that they expected him, when instead of going to look for him, 4 they immediately searched for a replacement.
Kidushin 33b and Shulchan Aruch (YD 244:13,14) require this for a Nasi, but not for a Chacham or Av Beis Din. Moreover, how can we learn from Moshe, the Adon ha'Nevi'im, who was also considered king, on to S'tam Chachamim? (PF)
See Torah Temimah, note 8.
Torah Temimah: Although Moshe was also a king, that title was only conferred upon him after he received the second Luchos. See Torah Temimah, who elaborates on the entire issue.
See Oznayim la'Torah.