The priests of the Old Covenant saw their duty as mediating between heavenly and earthly things, between God and his people. Since Christ is the “one mediator between God and men” (1 Tim 2:5), he perfected and ended that priesthood. After Christ there can be an ordained priesthood only in Christ, in Christ’s sacrifice on the Cross, and through a calling and apostolic mission from Christ.
A Catholic priest who administers the Sacraments acts not on the basis of his own power or moral perfection (which unfortunately he often lacks), but rather “in persona Christi”. Through his ordination, the transforming, healing, saving power of Christ is grafted onto him. Because a priest has nothing of his own, he is above all a servant. The distinguishing characteristic of every authentic priest, therefore, is humble astonishment at his own vocation.