“…In the morning, G-d will make known who is His, and who is holy, and He will draw them near to Him…” – Bamidbar 16:5

בֹּקֶר וְיֹדַע ה’ אֶת אֲשֶׁר לוֹ וְאֶת הַקָּדוֹשׁ וְהִקְרִיב אֵלָיו – במדבר טז, ה

Korach and his followers contested Moshe’s authority and his appointment of Aharon as the Kohen Gadol, the High Priest.  Moshe challenged them to come the next morning and offer ketores, incense, the most sacred of services in the Mishkan. Moshe warned them that in the morning, G-d Himself would make known “who is holy, and He will draw them near to Him.” Rashi explains that Moshe delayed the showdown until the next morning with the hope that in the meantime they might retract.

Moshe’s delay until morning also hinted to the ideal manner of teshuvah, repentance, which he hoped they would do. To be sure, a person’s sins can be atoned through one moment of sincere regret, even if the remorse is caused by fear of Divine retribution for his transgressions. This form of repentance, however, does not necessarily transform the individual; his fear of punishment is simply another form of his egocentric fixation on self-preservation and survival.

The ideal teshuvah is a repentance that is not motivated by any personal gain or protection. It stems simply from a pure love for G-d and a yearning to cleave to Him. This teshuvah refines and transforms the penitent’s life. His sincere observance of G-d’s commandments is no longer obscured by any personal pride or satisfaction, and therefore radiates G-dly light in his life and in the world around him.

Moshe therefore told Korach and his followers to wait until the morning light. He thereby expressed his hope that not only would they retract, but that their repentance would be an inspired and “morning-like” teshuvah that would illuminate their lives.

—Likutei Sichos vol. 4, pp. 1053-1054