On the Catholic Priesthood
Our Savior in associating with Himself certain men to continue the work of redemption reserved to Himself the direct and immediate action on souls. He works through the priest, who is only His minister and instrument. If the instrument works according to the required conditions, its action is free and produces the desired effect. But if the instrument is corrupt and wicked, its action is impeded and produces no effect.
Source: Jesus Living in the Priest, The General Idea of the Priest by Rev. Fr. Jacques Millet