5 Let them
be as chaff [mots] before [paniym] the wind [ruwach]: and let the angel [mal'ak]
of the LORD [Y@hovah] chase [dachah] them. KJV-Interlinear
5 Let them
be like chaff before the wind, with the angel of the LORD driving them away! ESV
Chaff is the empty and light portion of the grain stock, which is blown away by the wind or a gentle breeze, when the grain is tossed up into the air and the chaff is separated from it by the wind, and blown away. The grain is the good part and drops to the ground for collection and later use.
The chaff drifts away and is forever gone, lost, and ends up in the obscurity of the world. It cannot be identified or distinguished from the dust or any other particle of the earth.
Thus chaff is identified with the empty, the light, the useless, the worthless, the vain or vanity of the world.
The chaff of humanity includes all unbelievers who have no spiritual life, as well as all believers who disregard their spiritual obligations.
To chase them, is a military term, wherein when the enemy is in full retreat then you continue the pursuit until they are all killed or captured or otherwise removed the picture of life. And this is what God does and will have completed when history comes to its conclusion.