78 Men in Sacred Orders should gain an adequate knowledge of human affairs and a thorough knowledge of sacred doctrine that is in keeping with their abilities. Would that all pastors of souls would exert as much effort as the Cure of Ars did to overcome difficulties and obstacles in learning, to strengthen memory through practice, and especially to draw knowledge from the Cross of Our Lord, which is the greatest of all books. This is why his Bishop made this reply to some of his critics: "I do not know whether he is learned; but a heavenly light shines in him." (82)
Source: Sacerdotii Nostri Primordia (Vatican.va)