din klali and din prati

Our parsha opens with the count of the shevatim.  According to Ramban and others this tally was needed in order to asses the size of the army and prepare for conquest of Eretz Yisrael.  Sheivet Levi was not included in that count.  Rashi (1:49) explains: כדיי הוא לגיון של מלך להיות נמנה לבדו.  Sheivet Levi is the "king's legion," they are special, and therefore they get special treatment and are counted seperarely.

R' Chaim Elazari in his Nesivos Chaim wonders:

 איך יכול הוא להיות חשׁוב כּמו היוצא צבא להגנת ארץ 

How can it be that sheivet Levi is more chashuv than soldiers going out to fight for Eretz Yisrael?!  

He does not give an answer, but the point is not to come up with an answer  The point is the attitude raising such a question reflects, and that's something we need to think about and absorb. 

Rashi offers a second explanation as to why Levi was counted apart from everyone else: 

דבר אחר: צפה הקב״ה שעתידה לעמוד גזירה על כל הנמנין מבן עשרים שנה ומעלה שימותו במדבר. אמר: אל יהו אילו בכלל, לפי שהן שלי, שלא טעו בעגל.

Those who were counted were included in the death sentence given to the dor hamidbar for cheit ha'meraglim. Hashem wanted Levi excluded from that punishment, so he did not include them in the count.

M'mah nafshach: if sheivet levi was guilty of the same sin as everyone else, then why should they get off scott free just because they were not included in this count?  And if sheivet levi was not guilty, then even if they were counted, why should they receive punishment?  (See Sifsei Chachamim, also Eretz Tzvi from the Kozhiglover.  Also, see R' Baruch Mordechai Mizrachi's approach.  He  points out that even if you say כיון שניתן רשות למשחית אינו מבחין בין צדיקים לרשעים, one still must explain why honoring Levi by counting them separately removes that chashash. I think one can make a better argument that כיון שניתן רשות למשחית אינו מבחין בין צדיקים לרשעים is with respect to an onesh b'poel, not a gezeirah of what will happen down the road.) 

We find a similar question raised elsewhere by Ramban.  In Parshas Korach, Korach gathers his band of rebels in front of Ohel Moed.  Hashem then appears to Moshe and tells him  הִבָּ֣דְל֔וּ מִתּ֖וֹךְ הָעֵדָ֣ה הַזֹּ֑את וַאֲכַלֶּ֥ה אֹתָ֖ם כְּרָֽגַע׃ (16:21) Meaning, Hashem wanted to punish all of Bnei Yisrael, the entire עֵדָ֣ה.  Moshe responds  ק-ל אֱלֹקי הָרוּחֹ֖ת לְכׇל־בָּשָׂ֑ר הָאִ֤ישׁ אֶחָד֙ יֶחֱטָ֔א וְעַ֥ל כׇּל־הָעֵדָ֖ה תִּקְצֹֽף׃.  Why punish everyone for the bad deeds of the few.  Ramban writes:

 יש לשאול אם ישראל לא חטאו ולא מרדו ברבם, למה היה הקצף עליהם לאמר: ואכלה אותם כרגע. ואם גם הם מרדו כקרח וכעדתו, איך אמרו משה ואהרן: האיש אחד יחטא ועל כל העדה תקצוף.

It's a similar m'mah nafshach: if Bnei Yisrael are not guilty, why would G-d threaten to punish them?  And if they are guilty, how can Moshe argue that Korach alone deserves punishment?

My wife's grandfather, R' Dov Yehuda Shochet, develops the following yesod in a few places to answer questions like this (he discusses it in the context of the Ramban in Korach; I am extending it to the Rashi in our parsha): the Mishna tells us that on Sukkos we are judged by Hashem as to how much rain will fall; on Pesach we are judged as to how much wheat will grow; on Shavuos we are judged on how the fruit will grow; on Rosh haShana every person passes before Hashem and is judged for the year.  If every person's fate is decided on Rosh haShana, asks the Ran, then wouldn't that include (as we say in the Nesaneh Tokef tefilah) whether they will be rich or poor, how their crops will grow, etc.?  What need is there for a seperate period of judgment for each of the other items mentioned?  Ran answers that there are two levels of din -- that of the individual and that of the community.  On Pesach, Shavuos, and Sukkos, there is judgment of the community as a whole, whether in that country or locale they deserve a rainy year, a year with a bountiful harvest, a year with good crops.  On Rosh haShana, each individual passes before Hashem and is judged on an individual basis what his/her portion will be like for that year.  My wife's granfather writes that there are times when an individual may be worthy, but suffers because the community as a whole is judged harshly.  כיון שניתן רשות למשחית אינו מבחין בין צדיקים לרשעים  On the flipside, sometimes the community is unworthy, but the positive din of the individual can lift them up, e.g. Hashem would have spared the entire city of Sdom had there been but 10 tzadikim there.  Somehow, these two aspects of din work together to produce an equitable result.

When Hashem first judged the rebellion of Korach, it was through the lens of communal judgment, din klali, and hence the entire community was lumped together in one basket. Moshe davened for Hashem to look at the rebellion through the lens of din prati, on a more ganular level, allowing the merits of each individual aside from Korach's followers to tilt the scales (it's possible this is what Ramban means in his answer to the question - take a look).

Because sheivet Levi acted as a yotzei min ha'klal by the cheit ha'eigel, Hashem rewarded them midah k'neged midah by allowing the din prati of their sheivet to override the din klali on all others counted between 20 and 60 who died in the midbar.