Moshe suggested to Korach and his followers to perform a test to see whether indeed there lies any truth in their complaint. He told them to bring an offering of ketores, and so will Aharon, and accordingly, they will see whose will be accepted on High. Hence, they'll know whose position is correct. בוקר וידע ה' את אשר לו ואת הקדוש והקריב אליו tomorrow morning Hashem will inform who is to Him and who is sanctified for the Kehuna and He brought him close to Him. (טז ה)
Rashi quotes a Midrash which says that just as one cannot alter the seder of day and night, morning cannot be turned into night, or vice versa, so too one cannot change a person's position in life. One's personal circumstances have been preordained just like day and night. Here, this is what Moshe Rabbeinu is telling Korach - just like you can't alter the natural order of day, so too, you cannot change your circumstances.
Seforim explain that Korach didn't understand that he alone gains from the greatness of Moshe Rabbeinu. A certain measure of his success was only as a result of being close to Moshe, for being in his presence surely had an impact on him just as the entire generation were being impacted from being in Moshe's presence. Hashem has created the world in this manner, where the great ones in each generation are mashpia on the lesser. The layperson receives from the Talmud Chochom and the Talmud Chochom also receives from those greater than him. Through the lesser individuals looking up to, absorbing from, and appreciating the greater individuals in their times, they consequently also get elevated and can thus reach further.