This is a law of life. If a person works for another they are supposed to get payment for that work. That same law of payment applies in the spiritual realm.
Judgment is one of the biggest topics in the Scriptures.
Paul warned a group of intellectuals on Mars Hill of the coming judgment. Solomon warned of living our lives as we please without regard for the things of God. But God does not always wait until the end of life to pay off. We often face judgment right here. There is a payoff for sins both here and hereafter.