4 And it is this peculiar and singular power of Holy Scripture, arising from the inspiration of the Holy Ghost, which gives authority to the sacred orator, fills him with apostolic liberty of speech, and communicates force and power to his eloquence. For those who infuse into their efforts the spirit and strength of the Word of God, speak "not in word only but in power also, and in the Holy Ghost, and in much fulness."(12) Hence those preachers are foolish and improvident who, in speaking of religion and proclaiming the things of God, use no words but those of human science and human prudence, trusting to their own reasonings rather than to those of God. Their discourses may be brilliant and fine, but they must be feeble and they must be cold, for they are without the fire of the utterance of God(13) and they must fall far short of that mighty power which the speech of God possesses: "for the Word of God is living and effectual, and more piercing than any two-edged sword; and reaching unto the division of the soul and the spirit."(14) But, indeed, all those who have a right to speak are agreed that there is in the Holy Scripture an eloquence that is wonderfully varied and rich, and worthy of great themes. This St. Augustine thoroughly understood and has abundantly set forth.(15) This also is confirmed by the best preachers of all ages, who have gratefully acknowledged that they owed their repute chiefly to the assiduous use of the Bible, and to devout meditation on its pages.
Source: Providentissimus Deus (Vatican.va)