He hath swallowed down riches and he shall vomit them up again. The wicked man shall be made to disgorge his ill-gotten gains. Either fear, or remorse, or a judicial sentence will force him to make restitution (see Job 20:10).
God shall cast them out of his belly. Whatever is the immediate motive of the restitution: it will really be God's doing. He will cause the fear, or the remorse, or bring about the judicial sentence.