Albert Barnes Commentary Job 21:18

"That they are as stubble before the wind, And as chaff that the storm carrieth away?" — Job 21:18 (ASV)

They are as stubble before the wind - According to the interpretation proposed of the previous verse, this may be read as a question: “How often is it that the wicked are made like stubble? You say that God deals with people exactly according to their characters, and that the wicked are certainly subjected to calamities; but how often does this, in fact, occur? Is it a uniform law? Do they not, in fact, live in prosperity and arrive at a good old age?” It is not uncommon in the Scriptures to compare the wicked with stubble, and to affirm that they will be driven away, as the chaff is driven by the wind; see the notes at Isaiah 17:13.

The storm carrieth away - Margin, “stealeth away.” This is a literal translation of the Hebrew. The idea is that of stealing away before one is aware, as a thief carries off spoil.