Prevented from performing a mitzvah
ואתחנן אל-יקוק בעת ההיא…ויאמר יקוק אלי רב-לך אל-תוסף דבר אלי עוד בדבר הזה
I pleaded to Hashem at that time…Hashem said to me: “There’s a lot for you. Don’t continue to speak to Me about this matter any more”
Moshe, shortly before his death, explained to the people why their leader would not take them into the land of Israel. Instead, his successor Yehoshua would take charge. Moshe was punished for his prior transgression with dying before ever entering the land. He couldn’t take this quietly, and repeatedly prayed to Hashem to forgive him; to allow him to at least enter the land. Finally, Hashem responded with the phrase: “רב לך! There’s a lot for you! Don’t continue praying for this, as you will not enter.” Chazal pick up on this unusual expression “רב לך”, and note that Moshe used this exact same phrase to Korach and his band of rebels. He said “רב לכם בני לוי, There’s a lot for you, Levites”. In addition to noting this similarity, Chazal say ברב בישר ברב בישרוהו, because Moshe said רב לכם to Korach, Hashem said to him רב לך. This sounds like some sort of punishment. Chazal say similarly about Yehudah, who said: “הכר נא, Identify this” to his father Yaakov, trying to trick him into thinking his son Yosef was killed. Yehudah subsequently had his daughter-in-law say to him: “הכא נא, Identify this”. In that context, it’s clear that Yehudah committed a sin by saying this to his father. However, what was Moshe’s transgression? Korach and his band were trying to usurp Moshe’s Divinely given authority. Moshe had every right to rebuke them. Why was he subsequently punished with Hashem telling him: “רב לך, you will not enter the land of Israel”?
It would seem that Chazal are really informing us about something else. Regarding the episode of Korach and his rebellion, it truly could have been understood in a different light. Perhaps Korach and his followers had noble intentions. Maybe they simply wanted to achieve a closer relationship with Hashem, and serve Him in a more significant way. They wanted to be Kohanim, those who perform the Temple service, and not simply be Leviim. They didn’t have in mind honor, glory, and the opportunity to lord over the people. However, Moshe knew their true intentions. He told them, that if their intentions were pure, solely for the sake of Heaven, why were they demanding that they become Kohanim? What difference does it make? Did they in fact choose that they were born Leviim? Hashem decided that it would be so! It was clearly the role that Hashem had in mind for them. If they wanted to do more, it would be no different than anyone who intended to do a mitzvah, and was withheld from performing it. In such cases, Hashem considers it as if they in fact did perform the mitzvah. So why demand the promotion? It showed that their true intention was selfish: glory, honor, and authority.
One explanation of רב לך which Hashem said to Moshe is: there is tremendous good stored for you in the World to Come. Why was this Hashem’s response to Moshe’s request to enter the land? Chazal note that Moshe’s intention to enter the land of Israel wasn’t a physical desire. He didn’t seek to eat its fruits. Rather, he wanted to fulfill the mitzvos that can only be performed in the land. He wanted the merit associated with these mitzvos. Therefore, Hashem told him not to worry. He already has this merit stored for him in the next world. How so? Since he desires to fulfill these mitzvos, but is being prevented from doing so, it is considered as if he has fulfilled them. Consequently, he shouldn’t be upset that he has to die without entering the land.
This is exactly how Moshe responded to Korach when he said רב לכם. He informed them that Leviim have tremendous reward awaiting them, even though they aren’t Kohanim. If Korach and his group’s intentions were noble, they wouldn’t need to worry. The truth just happened to be that they had ulterior motives for their rebellion. This explanation provides a new meaning to Chazal’s statement: ברב בישר ברב בישרוהו, [Moshe] informed others with the word רב, [such that] Hashem informed him with the word רב. This isn’t meant to be understood as a punishment. בישר is understood along the lines of בשורות טובות, good tidings. Moshe told Korach the good that would’ve been in store for him. Therefore, Hashem gave him the same tidings: he would have tremendous reward in the World to Come.
 Based on Sheivet Sofer Al HaTorah UMoadim to Numbers 16:7, by the son of the Kesav Sofer and grandson of the Chasam Sofer
 Deuteronomy 3:23, 26
 Sotah 13b
 Numbers loc. cit.
 Sotah 10b
 This is a question that many commentaries struggle with. Most conclude it was a transgression on Moshe’s part. For example, Rav Chaim Shmuelevitz was wont to say that a person should have never-ending aspirations for spirituality, and Moshe shouldn’t have told Korach that he has enough. Hashem therefore told him that he too has enough, and will not get to enter the land of Israel
 מחשבה טובה מצרפה למעשה (Kiddushin 40a)
 Rashi to Deuteronomy 3:26. The Chumashim say that Rashi’s source is Sifrei Devarim § 29, but it’s more likely Tanchuma Yashan Hosafah LeVaeschanan § 1
 Sotah 14a
 ibid 13b
 I saw similarly in Divrei Yoel by the Satmar Rebbe to parshas Korach s.v. וז”ש הקב”ה למשרע”ה רב לך. This however can’t be how בישר is used regarding Yehudah and Tamar. See note 7
 This is similar to how Ben Yehoyada to Sotah 13b s.v. ברב בשר ברב בשרוהו explains it, that רב לכם was complimentary. Cf. Maharal’s Chiddushei Aggados ad. loc. who understands רב לכם to be insulting