Origen

“ But we may also learn from this, that in respect of the reasonings only which we reason within ourselves, we are sometimes convicted and reproached as being of little faith. And I think that just as a man commits adultery in his heart only, though not proceeding altogether to the overt act, so he commits in his heart the rest of the things which are forbidden. ”

“ As then he who has committed adultery in his heart will be punished proportionately to adultery of this kind, so also he who has done in his heart any one of the things forbidden, for example, who has stolen in his heart only, or borne false witness in his heart only, will not be punished as he who has stolen in fact, or who has completed the very act of false testimony, but only as he who has done such things in his heart. There is also the case of the man who while he did not arrive at the evil action, came short of it in spite of his own will. ”