A Change of Heart

וּבְנֵי אֱלִיאָב . . הוּא דָתָן וַאֲבִירָם קְרִיאֵי הָעֵדָה אֲשֶׁר הִצּוּ עַל מֹשֶׁה וְעַל אַהֲרֹן בַּעֲדַת קֹרַח בְּהַצֹּתָם עַל ה': וַתִּפְתַּח הָאָרֶץ אֶת פִּיהָ וַתִּבְלַע אֹתָם וְאֶת קֹרַח . . וּבְנֵי קֹרַח לֹא מֵתוּ (במדבר כו, ט-יא)

The sons of Eliav… Dasan and Aviram, the chosen of the congregation who incited against Moshe and Aharon in the assembly of Korach, when they incited against G-d. And the earth opened its mouth and swallowed them and Korach… Korach’s sons, however, did not die. (Bamidbar 26:9-11)

Rashi (26:11) explains that Korach's sons were from the original conspirators of the rebellion, but during the dispute they contemplated repentance. Therefore, an elevated area was set apart for them underground, and they stayed there. Eventually, they were allowed to leave and rebuild their families, as we find that Shmuel the Prophet was from among their descendants (see Rashi to 16:7). 

This explains why the sons of Korach are mentioned at this point, between the reckoning of the tribe of Reuven and Shimon. Why not mention this fun fact later, when recording the families of the tribe of Levi who would enter the land – among whom “the family of the descendants of Korach (26:58)” is listed?

Their unusual mention together with Dasan and Aviram must be specifically to teach us about their comparison. Dasan and Aviram were the original conspirators who stirred the entire controversy – and the sons of Korach were just as bad, having been the lead masterminds in plotting the rebellion.        

At the same time, however, the Torah teaches us the remarkable power of Teshuva, repentance. The sons of Korach were equally responsible and guilty for the entire showdown with Moshe. Even when they realized their mistake they didn’t abandon the fight, but merely contemplated repentance. Yet these hirhurei teshuva, thoughts of remorse, were alone sufficient to spare them of the brunt of punishment that met the other parties to the crime! Despite their lowly state, through teshuva they merited to rebuild families that would enter the Land of Israel, and eventually see the most righteous of offspring. 

—Likutei Sichos vol. 33, pp. 172-174