'Working' in the Bible

For what does a person gain from everything that he accomplishes and from his inner life struggles that he undergoes while working on earth?

Sweet is the sleep of a working man, whether he eats a little or a lot, but the excess wealth of the rich will not allow him to rest.

Sow your seed in the morning, and don't stop working until evening, since you don't know which of your endeavors will do well, whether this one or that, or even if both will do equally well.