On the verse "And they fell on their faces," Rashi quotes: "G‑d of the spirits" and explains: "Knower of thoughts. Your attribute is not like that of a human king. A human king, when a part of his kingdom rebels against him, does not know who the sinner is. Therefore, when he is angry, he punishes all. But You, before You all thoughts are revealed, and You know who the sinner is."
Simply put, Rashi's intention is to clarify that "G‑d of the spirits" does not refer to physicality, but rather to thoughts. Thus, "G‑d of the spirits" means G‑d who knows thoughts. (As we find in the previous portion: "But My servant Caleb, because he had a different spirit with him," where the term "spirit" refers to thought.) The proof for this is that only with this understanding is the connection between the beginning of the phrase "G‑d of the spirits" and the continuation "Shall one man sin, and You be angry with the entire congregation?" understood. Because since the Holy One, blessed be He, knows thoughts, He knows who the sinner is and upon whom to be angry. But if we were to say "G‑d of the souls," it would not be understood: what is the relevance of "G‑d of the souls" as a preface to "Shall one man sin, and You be angry with the entire congregation?"
Therefore, Rashi continues: "Your attribute is not like that of a human king, etc., but You know who the sinner is." This means that according to this explanation, "G‑d of the spirits" refers to the knower of thoughts. This is the necessity for Rashi's interpretation.
We need to understand, however, the argument of Moshe in this context. It would seem appropriate to bring a parable similar to that regarding Sodom: "Will You indeed sweep away the righteous with the wicked?" For even a human king, if he rules with justice and fairness, would not punish many people for the sin of one individual. Instead, he would appoint a judge, etc., to investigate and determine who the sinner is. And even if it is impossible to determine who the guilty party is, it still requires explanation—would a just king punish everyone simply because it was not clarified who the guilty party is?
Rashi begins with the phrase "a part of his kingdom rebels against him" and concludes with "who the sinner is." Rashi concludes with "he does not know who the sinner is," which is different from the opening "a part of his kingdom rebels against him."
G‑d said, "You have spoken well. I know and will make known who sinned and who did not sin." This also requires clarification:
a) What is Rashi's intention in this explanation, where instead of "shall one man sin" mentioned in the verse, he writes "who the sinner is" and adds the phrase "and You be angry with the entire congregation"—seemingly, there is no additional explanation here.
b) If Rashi's intention is to explain (in whatever manner) "shall one man sin" and "You be angry with the entire congregation," he should have quoted these words or at least hinted at them with "etc."
c) What is Rashi's intention in adding the matter: "G‑d said, etc., who sinned," and furthermore,
d) In response to Moshe's argument, G‑d said to Moshe: "Separate yourselves from among this congregation," and the verse explains the punishment that befell Korach, Dathan, and Abiram based on this.
It is not understood what Rashi means when he writes that the Holy One, blessed be He, said, "You have spoken well," implying that G‑d agrees with Moshe's argument that "shall one man sin" (and Rashi quotes these words) — yet G‑d informed that not one, but three sinned. The phrase "I know" seems superfluous, as the novelty is only in "I will make known." Especially since Rashi adds this to the language of the Midrash.
In the general context of the matter: In the preceding verses, it is mentioned several times that many people participated in Korach's dispute against Moshe and Aharon — "And they rose up... two hundred and fifty men from the children of Israel," "and they gathered against Moshe and Aharon," and Moshe spoke "to Korach and to all his assembly," and he also rebuked "all his assembly." Until he said, "You and all your assembly who are gathered against the L‑rd." In Rashi's commentary, it is stated that this was already their fourth transgression: they sinned with the Golden Calf, etc. From all this, it is evident that not only one person sinned in this dispute (even according to Moshe's view) — so how could Moshe say, "Shall one man sin?"
It is possible to say that Moshe drew the people of the assembly with his words, intending for their benefit, etc., until he involved them in complaints against Moshe and Aharon. This is evident regarding the main participants in the dispute, who are Dathan and Abiram, and "two hundred and fifty men from the children of Israel," as Rashi explains: "Because they were from the tribe of Reuben (from which Dathan and Abiram came, etc., and the majority of the two hundred and fifty men), who dwelt... adjacent to Kehat and his sons... they joined Korach in his dispute." This means that their participation in the dispute came through Korach enticing and inciting them until it seemed to them that his intention was correct. But in essence, without Korach's enticement, they would not have entered this dispute.
(And although certainly a person cannot justify himself with this excuse — that he is not at fault for doing something improper because he was enticed by someone else — for a person must distance himself from the wicked and also be firm in his resolve not to be swayed by enticements, etc. — nevertheless, in practice, they did not dispute Moshe and Aharon except under Korach's influence.)
However, since "a part of the kingdom" rebelled against the king, it is likely that among them was someone (at least one) who incited them and led them to this transgression — and in this regard, there was indeed a rebellion against the king. This is what Rashi writes: "He does not know who the sinner is" (in the singular) — meaning the inciter and cause of the transgression. In contrast, "a part of the kingdom" cannot be called "sinners," but rather there is a "transgression" here.
Therefore, in the case of a mortal king, since he does not know who the sinner is, he would punish them all, for in practice, they all transgressed against him. But You, before whom all thoughts are revealed, know who the sinner is. Therefore, it is not appropriate that only those who "transgressed" should be punished with the severe punishment of the sinner.
This argument of Moshe clarifies and interprets the words of the verse, and it is not a separate statement. As printed, it continues from the previous: "You know who the sinner is" — "Shall one man sin" (but the rest of the people only "transgressed"), and You (who knows thoughts) will be angry with the entire congregation. In response to Moshe's argument, G‑d said, "You have spoken well," meaning in regard to Moshe's general argument that only the "sinner" should be punished and not those who only "transgressed." However, concerning the specific matter, it is not as Moshe thought and assumed that there is one sinner, but rather "I know" and will make known. And it is explained in the verse, and Rashi writes that in some places, the punctuation mark is missing (which separates the words that Rashi quotes from the Midrash) in the words "Shall one man sin."
“Who sinned” — it was not only Korach who sinned, but also Dathan and Abiram sinned (aside from the rest of the congregation). This is why G‑d said, “Separate yourselves from around the dwelling of Korach, Dathan, and Abiram,” because all three of them are “sinners.”
The lesson for a person from this Rashi in the inner dimensions of the matters is as follows: In the parsha, it is recounted that Moshe sent to call Dathan and Abiram, but they refused to come and responded with great audacity, “Is it a small thing that you have brought us up... to kill us in the wilderness?” and “Will you gouge out the eyes of these men?” until “Moshe was very angry.” This shows that their participation in the dispute was not merely a mistake or a lapse, but they were indeed sinners. Nevertheless, Moshe Rabbeinu judged them favorably and said, “Shall one man sin.”
From this, we learn how much each person (since within each person there is an aspect of Moshe Rabbeinu) must work to instill this trait within themselves — to judge their fellow favorably. Even when a friend's conduct seems to negate any justification, one must still find merit in them. As a result, one will also do everything possible to bring them back and set them on the right path.