Romans 4:4

Now to him that worketh is the reward not reckoned of grace, but of debt.

The verse draws a sharp contrast between two ways a reward can be reckoned: if it is gained by working for it, it is counted not as grace but as a debt that is owed. To make faith together with works the purchase price of salvation would put the Creator under obligation to the creature, turning salvation in part into wages earned and owed as a debt, on exactly the same footing as doing penance for sins. Righteousness and salvation are not earned in this way, for no fallen person by good works or creature merit can change his standing before God or secure God's gift to himself, and the merit of good works can never procure eternal life, not even when a rich man offers money and possessions to the Lord.

Because the reward is not earned, no one has ground to boast, to claim it as a right, or to regard himself as more privileged than another. Since man cannot merit salvation, it is wholly of grace, a wholly free gift received by the sinner as he receives and believes in Jesus, received by grace through faith. In this the verse teaches justification by faith, setting that truth beyond controversy. It belongs to the teaching that Christ's righteousness is imputed to those who hunger and thirst for it.