Priority of Justification in Good Works

10. In this way we can admit not only that there is a partial righteousness in works, (as our adversaries maintain,) but that they are approved by God as if they were absolutely perfect. If we remember on what foundation this is rested, every difficulty will be solved. The first time when a work begins to be acceptable is when it is received with pardon. And whence pardon, but just because God looks upon us and all that belongs to us as in Christ? Therefore, as we ourselves when engrafted into Christ appear righteous before God, because our iniquities are covered with his innocence; so our works are, and are deemed righteous, because every thing otherwise defective in them being buried by the purity of Christ is not imputed. Thus we may justly say, that not only ourselves, but our works also, are justified by faith alone. Now, if that righteousness of works, whatever it be, depends on faith and free justification, and is produced by it, it ought to be included under it and, so to speak, made subordinate to it, as the effect to its cause; so far is it from being entitled to be set up to impair or destroy the doctrine of justification that it is what it is.

John Calvin, Institutes of Religion - Book 3.17.10