18 What he toiled for he must give back uneaten; he will not enjoy the profit from his trading.

Read Job 20:18 Using Other Translations

That which he laboured for shall he restore, and shall not swallow it down: according to his substance shall the restitution be, and he shall not rejoice therein.
He will give back the fruit of his toil and will not swallow it down; from the profit of his trading he will get no enjoyment.
They will give back everything they worked for. Their wealth will bring them no joy.