23 The Catholic priest is minister of Christ and dispenser of the mysteries of God in another way, that is, by his words. The "ministry of the word" is a right which is inalienable; it is a duty which cannot be disallowed; for it is imposed by Jesus Christ Himself: "Going, therefore, teach ye all nations . . . teaching them to observe all things whatsoever I have commanded you." The Church of Christ, depository and infallible guardian of divine revelation, by means of her priests, pours out the treasures of heavenly truth; she preaches Him who is "the true Light which enlighteneth every man that cometh into this world"; she sows with divine bounty that seed which is small and worthless to the profane eyes of the world, but which is like the mustard seed of the Gospel. For it has within itself power to strike strong deep roots in souls which are sincere and thirsting for the truth, and make them like sturdy trees able to withstand the wildest storms.
Source: Ad Catholici Sacerdotii (Vatican.va)