ויביאו את-המשכן אל-משה וגו’ הוקם המשכן: ויקם משה את-המשכן וגו’
[The people] brought the Mishkan to Moshe…and the Mishkan was erected. Moshe erected the Mishkan…
After all of the materials were collected, tapestries woven, and implements constructed, the Mishkan, the portable Temple, was ready to be assembled. We are told that the people brought the Mishkan to Moshe. What is this referring to? All of the vessels? All of the tapestries? Why did they bring it to him? Shouldn’t they have brought everything to the craftsmen behind the Mishkan? Wasn’t it their job to finish the construction? To address all of these questions, Rashi brings an interesting idea from our Sages. It’s based on a verse which appears later, that the Mishkan “was erected”, which sounds passive. Immediately following this verse, we are informed that Moshe erected the Mishkan all by himself. Which one was it?
We are taught that the Jews became nervous after the construction of the Mishkan was completed. Hashem’s presence hadn’t descended yet. They realized that they had to finish its assembly, starting with erecting the beams of the Mishkan. They approached the craftsmen behind the Mishkan for them to erect these beams. The craftsmen tried and tried, but couldn’t figure out how to erect them. They brought them to Moshe with the hopes that he could help. He was also at a loss for how he could do it. Hashem immediately reassured him that if he makes the effort, he will be successful. He went through the motions, and Hashem performed a miracle to help him get the job done.
This Midrash elaborates on why it was that no one was able to erect the Mishkan, and only Moshe was successful. We are told that everyone had a hand in contributing towards the Mishkan, or helping construct it. Moshe had done nothing towards its creation, and he was feeling upset about it. What was he thinking? He’ll let the other people donate first, and whatever was left over, he’ll contribute himself. It ended up being that everything was donated before Moshe could get involved. Hashem made it such that no one could erect the Mishkan, giving Moshe an opportunity to contribute. He alone would be able to erect it, and despite it requiring a miracle, Moshe was given full credit.
It’s interesting to contrast this story with a similar one brought in last week’s parsha. We are taught that the princes, the leaders of the twelve tribes, delayed in providing a contribution towards the Mishkan. Their plan was to let other people donate first, and whatever would be left over they would fill the gaps. What happened was everything had been provided for, and they were left with nothing to contribute for the Mishkan. In the end they provided special stones to be used with the Kohen Gadol’s garments, but nothing for the Mishkan itself.
In both cases, with Moshe and the princes, they refrained from contributing towards the Mishkan. They had the exact same thought process. However, they both had vastly different outcomes. Moshe was rewarded with a miracle where he was able to erect the Mishkan singlehandedly. What happened with the princes? We are taught that they were punished for their laziness. Usually, the word princes is spelled נשיאים, however in one verse it is spelled without the י, as נשיאם. This loss of the letter י was the consequence of their lack of action. Why were the two inactions treated differently? Seemingly they both failed to contribute anything to the Mishkan. Why was Moshe rewarded, yet the princes punished?
We are forced to find some sort of distinction between the guilty feelings of the princes and those of Moshe. The guilt of the princes must have been on a lower level. Perhaps they were worried that people would look down on them for their inaction. As the leaders of the generation, they should have been one of the first to donate. These concerns are what pained them. However, Moshe’s guilt was entirely for the sake of heaven. His pain was in fact much more acute, as he was the only one who the whole time had an accounting of the materials that had been donated. He always knew how much was left to donate, and felt that he still had the opportunity. The sense of a lost opportunity was much greater for him. Since Hashem’s attribute of Good is greater than His attribute of Bad, not only was Moshe not punished for his appropriate guilt, he was even rewarded for it. Hashem performed a miracle, and gave him a hand in the Mishkan.
 Based on various sources that I found and collected
 Exodus 39:33, 40:17,18
 To ibid 39:33
 Midrash Tanchuma Pekudei § 12. A shorter version appears in Shemos Rabbah 52:4
 Rashi says שלא היו יכולין להקימו, and then says מחמת כבד הקרשים שאין כח באדם לזקפן. The simple and I believe the most common understanding of Rashi is that the beams, which were very large and plated with gold, were too heavy for anyone to lift. That’s why it was a miracle that Moshe lifted them, as we will see. This is at least the understanding of Mizrachi, Nachalas Yaakov, Maskil L’Dovid, and Sifsei Chachamim ad. loc. However, the language of the Midrash Tanchuma loc. cit. says ולא היו יודעין ולא היו יכולין להעמידו. It doesn’t sound like it was a strength issue but a lack of knowledge of how to lift them successfully. Also, in Shemos Rabbah loc. cit. it says כמה חכמים היו שם ובאו להם אצל משה ולא היו יכולין להקימו and שעשו את המשכן ולא היו יודעין לישבו. Therefore, Be’er BaSadeh ad. loc. suggests that due to the dimensions and weight of the beams, even after successfully erecting them, they would easily fall down. While everyone was able to lift them, no one could figure out how to keep them standing. Only Moshe realized that the crossbeam, which miraculously bent at the corners (see Targum “Yonasan” to Exodus 26:28 and Shabbos 98b), was necessary to keep them up, and only Moshe was successful at installing it. Be’er BaSadeh is shocked that none of the other commentaries picked up on this, and tries to squeeze this understanding into the words of Rashi. Although, the language of והוא עומד מאליו (see next note) doesn’t quite sound like this explanation
 The Midrash and Rashi say that the Mishkan stood by itself, which sounds like it was through a miracle. One could ask that if it required a miracle to erect, and only Moshe was seemingly given this miracle, how did the Leviim reconstruct the Mishkan throughout their travels in the wilderness? The Mizrachi, brought by Sifsei Chachamim loc. cit., says that once Moshe was appeased, there was no longer a reason to withhold this miracle from the others. It miraculously erected itself throughout their journeys for anyone. Biur HaAmarim ad. loc. adds that this was possible once the Divine Presence rested amongst the Jews and within the Mishkan. However, the Nachalas Yaakov, brought by Sifsei Chachamim loc. cit., asks that it’s clear from Shabbos 92a that Moshe was ten amos tall, so he should have been able to lift the beams without a miracle. The Maskil L’Dovid doesn’t understand how being ten amos tall would necessarily mean he would be super strong. Cf. the Maharal in his Chiddushei Aggados to Bava Metzia 84a (amongst other places), who says Moshe being ten amos tall isn’t meant to be taken literally, but rather is a reference to his spiritual stature. See also Rav Hartman’s note to Maharal’s Gevuros Hashem Chapter 18 fn. 19. In any event, according to the Be’er BaSadeh loc. cit. the question doesn’t get started
 Peirush Kadmon ad. loc. § 21. Eitz Yosef ad. loc. brings the same explanation from someone called Mefaresh Rishon. Perhaps it’s the same source. Avraham Ezkor ad. loc. cites this from המפרש שם. However, see note 9
 Rashi to Exodus 35:27, quoting Midrash Tanchuma loc. cit. It also appears in Bamidbar Rabbah 12:16. It’s almost as if the Midrash Tanchuma wants to contrast the two stories, as they’re brought together
 Eitz Yosef loc. cit. actually rejects the explanation of Mefaresh Rishon loc. cit. because of this very question
 Avraham Ezkor loc. cit.
 Tosefta Sotah 4:1; Sotah 11a
 See Kesav Sofer to Exodus loc. cit., who suggests that the intent of the princes (and we can add, Moshe) was like the opinion of the Teshuvos Chacham Tzvi § 106, that it’s preferable to perform a mitzvah later if it will be done in a more optimal way (מצוה מן המובחר), yet they were mistaken as the halacha follows the Radvaz 1:13 (4:1087) (the Kesav Sofer cites the dispute between the Chacham Tzvi and the Mishneh LaMelech to Mishneh Torah Hilchos Megillah 1:11. More precisely, the editor of the Mishneh LaMelech, Rav Yaakov Culi, author of the Yalkut Meam Loez, points out that according to what the Mishneh LaMelech writes, the Chacham Tzvi has no question on the Radvaz), that it’s better to do the mitzvah at the first possible moment. The Mishnah Berurah to Shulchan Aruch Orach Chaim 90:9 § 28 rules like the Radvaz, and the Ba’er Heitev ad. loc. § 11 also seems to lean this way. Cf. Sha’arei Teshuva to Shulchan Aruch Orach Chaim 651:8 § 17, who only brings the Chacham Tzvi. In any event, the Kesav Sofer seems to say that the princes were punished for their incorrect ruling. However, perhaps we can suggest according to this approach of the Avraham Ezkor that there was nothing wrong with their ruling. Either the halacha does follow the Chacham Tzvi, or at that time the matter wasn’t definitive enough to be punished. At the end of the day, both Moshe and the princes, despite their good intentions, were unable to contribute to the Mishkan. Everything had been donated already. They were expected to feel sad at this lost opportunity. Moshe indeed felt this way, and was rewarded. Not so the princes. The Avraham Ezkor suggests that their pain wasn’t as sincere as Moshe’s, and for that they were punished