Rashi: The strength, that they coerced the poor and stole from them, and strengthened themselves with the money - "v'Chavrei Ganavim" (23) - that money will be like chaff that is shaken off flax. It is light, and burns easily.

Radak: This refers to the idols and those who serve them. The strength in idols - like "Etz Lo Yirkav Yivchar" (they chose good wood that will not rot for their idols) - what burns quickly will help their strength. They will be like chaff, which burns easily due to a spark. And so it was - Nevuzaradan burned all houses of Yerushalayim; there was idolatry inside.

Malbim: The theft itself that they took by force will resemble flax chaff prepared to burn easily from a flame.

Rashi: The one who makes that strength will be a spark of fire, and they will burn each other.

Rashi citing Targum Yonasan: The work of their hands. Rashi - this is not from Hebrew, for if so, there should have been a Chataf Kamatz ¹ [under the Pei], and it would be an expression of Pa'ul (the work). Now that it has a Cholem, it refers to the worker.

Radak: The one who made the idol, he caused the burning, just like the spark burns the chaff. A spark that ignited chaff, both of them extinguish soon, for a spark is not an enduring flame; it extinguishes after a short time. Also chaff extinguishes after a short time. So the makers of the idol and the idol will perish together. In the Churban of Yerushalayim, the idols burned with the houses, and those who serve and make the idols were killed.

Malbim: The one who makes the theft, i.e. the robber. He will be like a spark that burns the chaff. They will burn together and terminate together. This is a wondrous metaphor; the sin destroys the one who does it. The sinner himself prepares the sin and makes it a tool of destruction that will destroy and eradicate him.

Rashi citing Targum Yonasan: No one is concerned for it.