66 The seminary is and should be the apple of your eye, Venerable Brethren, who share with Us the heavy weight of the government of the Church; it is, and should be, the chief object of your solicitude. Careful above all should be the choice of superiors and professors; and, in a most special manner, of the spiritual father, who has so delicate and so important a part in the nurture of the priestly spirit. Give the best of your clergy to your seminaries; do not fear to take them from other positions. These positions may seem of greater moment, but in reality their importance is not to be compared with that of the seminaries, which is capital and indispensable. Seek also from elsewhere, wherever you can find them, men really fitted for this noble task. Let them be such as teach priestly virtues, rather by example than by words, men who are capable of imparting, together with learning, a solid, manly and apostolic spirit. Make piety, purity, discipline and study flourish in the seminary. With prudent foresight, arm and fortify the immature minds of students both against the temptations of the present, and against the far more serious perils of the future. For they will be exposed to all the temptations of the world, in the midst of which they must live, "that they save all."
Source: Ad Catholici Sacerdotii (Vatican.va)