But the faith by which we are cleansed from sin is not that faith which can exist side by side with sin, the faith called formless, but faith formed, that is to say, faith made alive by charity. So that the Passion of Christ is not through faith applied merely to our understanding but also to our will. Again, it is from the power of the Passion of Christ that the sins are forgiven which are forgiven by faith in this way.
--St. Thomas Aquinas
