Commentary for Numbers 16:34

נסו לקולם [AND ALL ISRAEL …] FLED AWAY AT THEIR VOICE — i.e. on account of the sound that broke out because of their being swallowed up.

נסו לקולם, when they cried out at the time when they fell into the bowels of the earth. Compare Jeremiah 49,21 לקול נפלם רעשה ארץ, “the earth itself shook when it heard the sound of their downfall.”

נסו לקולם, “they fled when they heard their sound.” This appears to mean that as Korach and companions descended into the bowels of the earth they called out in repentance: “Moses is true and his Torah is true,” as our sages reported Rabbi bar Chanah as hearing over a site reputedly the point where all of this took place (Baba Batra 74). According to the report of the Talmud, an Arab guide took Rabbi bar Chanah to a site at which thin smoke emerged from the earth on top of two small cracks in the surface of the earth. The Arab placed some wet wool on top of the site, ignited it, and told the Rabbi to listen carefully. When Rabbi bar Chanah put his ear to it he could hear the confession of Korach that Moses and his Torah are true whereas he and his crowd were liars. According to that Arab this phenomenon could be observed every thirty days. This was a demonstration of the justice meted out in purgatory, i.e. to make the guilty confess their erstwhile sins.