John Gill Commentary Psalms 106:18

"And a fire was kindled in their company; The flame burned up the wicked." — Psalms 106:18 (ASV)

And a fire was kindled in their company
This seems to be the company of Korah, or however a part of it, the two hundred and fifty men that had censers, and so were of the Levitical race, as Korah was; this fire came from the Lord out of heaven.

The flame burned up the wicked ;
the two hundred and fifty men with censers, (Numbers 16:35) , this was an emblem of that fire which shall consume those that hurt the witnesses; or of that vengeance of eternal fire which wicked men will suffer for ever.