Read Numbers 26:10 Using Other Translations
And the earth opened her mouth, and swallowed them up together with Korah, when that company died, what time the fire devoured two hundred and fifty men: and they became a sign.
and the earth opened its mouth and swallowed them up together with Korah, when that company died, when the fire devoured 250 men, and they became a warning.
But the earth opened up its mouth and swallowed them with Korah, and fire devoured 250 of their followers. This served as a warning to the entire nation of Israel.