לָכֵן֩ כֶּאֱכֹ֨ל קַ֜שׁ לְשׁ֣וֹן אֵ֗שׁ וַחֲשַׁ֤שׁ לֶֽהָבָה֙ יִרְפֶּ֔ה שָׁרְשָׁם֙ כַּמָּ֣ק יִֽהְיֶ֔ה וּפִרְחָ֖ם כָּאָבָ֣ק יַעֲלֶ֑ה כִּ֣י מָאֲס֗וּ אֵ֚ת תּוֹרַת֙ יְהוָ֣ה צְבָא֔וֹת וְאֵ֛ת אִמְרַ֥ת קְדֽוֹשׁ־יִשְׂרָאֵ֖ל נִאֵֽצוּ׃
Therefore as the tongue of fire devoureth the stubble, And as the chaff is consumed in the flame, So their root shall be as rottenness, And their blossom shall go up as dust; Because they have rejected the law of the LORD of hosts, And contemned the word of the Holy One of Israel.
Ibn Ezra on Isaiah
קש Stubble. Objective case. לשון אש The flame of fire.33A. V., The fire. Subject.
Rashi on Isaiah
as a flame of fire consumes stubble [lit.] as consuming the stubble a flame of fire.