וּבְאַחַ֖ת יִבְעֲר֣וּ וְיִכְסָ֑לוּ מוּסַ֥ר הֲבָלִ֖ים עֵ֥ץ הֽוּא׃
他們在一件事上顯得愚昧糊塗：虛空之物所給的教導，不過是木頭罷了。
Rashi
But with one thing they are brutish i.e., the heathens, and what is that one thing? Their vanities of wood for which they will be punished, and they will be punished for it. יבערו is an expression of foolishness, so is ויכסלו.