Jamieson, Fausset and Brown on Ecclesiastes 7:6

6. crackling--answers to the loud merriment of fools. It is the very fire consuming them which produces the seeming merry noise (Joe 2:5). Their light soon goes out in the black darkness. There is a paronomasia in the Hebrew, Sirim ("thorns"), Sir ("pot"). The wicked are often compared to "thorns" (2Sa 23:6; Na 1:10). Dried cow-dung was the common fuel in Palestine; its slowness in burning makes the quickness of a fire of thorns the more graphic, as an image of the sudden end of fools (Psa 118:12).