Charles H. Spurgeon on Psalms 106:18

And a fire was kindled in their company; the flame burned up the wicked. The Levites who were with Korah perished by fire, which was a most fitting death for those who intruded into the priesthood, and so offered strange fire. God has more than one arrow in his quiver, the fire can consume those whom the earthquake spares. These terrible things in righteousness are mentioned here to show the obstinacy of the people in continuing to rebel against the Lord. Terrors were as much lost upon them as mercies had been; they could neither be drawn nor driven.