After naming the families of the tribe of Reuven that would enter the Land of Israel, the Torah recounts that Dasan and Aviram (who were from the tribe of Reuven) perished along with Korach when they incited a rebellion against Moshe and were swallowed by the earth. The Torah then notes that the sons of Korach did not die in that episode.

Rashi (Bamidbar 26:11) explains that the earth swallowed Korach’s sons together with him, but “an elevated area was set apart for them underground, and they stayed there.” Eventually, they were allowed to leave and rejoin the community (see Rashi on Bamidbar 16:7). Although they had been from the original conspirators of the rebellion, they were spared from death because during the conflict they inwardly regretted what they had done.

The degree of Korach’s sons involvement in the conflict is hinted by the placement of the verse, “Korach son’s did not die,” alongside the description of Dasan and Aviram’s role in inciting the dispute.  Their mention alongside Dasan and Aviram, (and not later, when the Torah names the descendants of Korach among the families of Levi’im who would enter the Land [see Bamidbar 26:58]) indicates that like Dasan and Aviram, the sons of Korach played a lead role in plotting and inciting the conflict. Nevertheless, the Torah states that the sons of Korach were not punished like the others, because ultimately they repented—at least inwardly.

From here we see the remarkable power of teshuvah, repentance. Korach’s sons not only took part in his dispute, they were among its original conspirators. Even when they recognized their wrongdoing, they did not openly abandon the rebellion. Yet their thoughts of remorse were alone sufficient to save them from dying with the other conspirators, allowing their families to enter the Land of Israel.

—Likutei Sichos, vol. 33, pp. 172-175