What are the implications of the words "Al Hashem"?
Rashi: It implies that their quarrel was not against them - Moshe and Aharon 1 - but against Hashem, since Moshe's appointment of Aharon as Kohen Gadol was at the behest of Hashem.
Seforno: Moshe was warning Korach 'I am casting my lot on Hashem - that He should defend my honor and that of Aharon.' 2
What is the exact translation of "Atah ve'Chol Adascha ha'No'adim al Hashem ... "?
Ramban #1 (explaining Rashi): 'You and your congregation, who are assembling with you, it is against Hashem that you are assembling, not against Aharon'. 1
Ramban #2 (citing Ibn Ezra): The 'Hey' is redundant, and the Pasuk reads 'You and your congregation are grumbling against Hashem ... '.
Ramban #3: With reference to Pasuk 7, Moshe is saying 'You and your congregation, who are assembling against Hashem and not against Aharon, appear before Hashem tomorrow'.
Ramban: It is a 'short Pasuk', incorporating something that is self-understood.
Why did Moshe find it necessary to repeat "Atah ve'Chol Adascha" since he already began addressing them above in Pasuk 5?
Ramban: Because in Pasuk 8, he addressed Korach exclusively, he needed to reintroduce them into his instructions.
Why didn't Korach answer Moshe?
Hadar Zekenim: Korach was a clever Rasha. He knew that Moshe is a great Chacham. If I answer him, he will refute me, and I will need to accede.