6 But as the Church was to last to the end of time, something more was required besides the bestowal of the Sacred Scriptures. It was obviously necessary that the Divine Founder should take every precaution, lest the treasure of heavenly-given truths, possessed by the Church, should ever be destroyed, which would assuredly have happened, had He left those doctrines to each one's private judgment. It stands to reason, therefore, that a living, perpetual "magisterium" was necessary in theChurch from the beginning, which, by the command of Christ himself, shouldbesides teaching other wholesome doctrines, give an authoritative explanation ofHoly Writ, and which being directed and safeguarded by Christ himself, could byno means commit itself to erroneous teaching. God has provided for these needsmost wisely and effectively through His Only-begotten Son Jesus Christ, Whoplaced the true sense of the Scriptures in safety, when He laid upon HisApostles as His primary and most momentous injunction, not to devote themselvesto writing, nor to spreading the volumes of the Old Testament indiscriminatelyand unguardedly among the multitude, but to teach all nations with the livingvoice, and to lead them by speech to the knowledge and profession of HisHeavenly doctrine: "Going into the whole world preach the Gospel to everycreature." (Mark xvi. 15.) But the supreme teaching authority was committedto one, on whom, as on its foundation, the Church must rest. For Christ when Hegave the keys to Peter, gave him at the same time the power to govern those whowere charged with the "ministry of the word:" "Confirm thyBrethren" (Luke xxii. 32). And since the faithful must learn from the"magisterium" of the Church whatever pertains to the salvation oftheir souls, it follows that they must also learn from it the true meaning ofScripture.
Source: Caritatis Studium (Vatican.va)