11 But it is necessary that your paternal care extend further, namely to the assistance of priests in the exercise of their duties. Skillfully and sweetly, as becomes your love, see to it that they are not exposed to worldly temptations and that they are not led by selfish desires or concern for secular affairs. See to it that they excel in virtue, providing an example of deeds well-done. Further, see to it that they never fail in their devotion to prayer and that they approach the sacred mysteries spotlessly. When supported and strengthened by these defenses, they will gladly fulfill their daily sacred duties and fittingly turn to the studious cultivation of the spirits of their people, especially by the ministry of word and sacraments. - But to renew the strength of soul which human weakness does not allow to flourish constantly, nothing seems more effective than that they retire from time to time to meditation, devoting all of their time solely to God and themselves. This is the custom in other places and has proven very successful. Furthermore you will easily and spontaneously get to know the talents and the habits of individual priests as you go about administering your dioceses. You will also learn what you have to do by way of prohibition in this matter, and what evils have to be eradicated. To do this and to save ecclesiastical discipline from violation, you must use the just severity of canon law where necessary. All must understand that both the priesthood and the various grades of dignity are no more than a reward for useful labors. For this reason they are reserved for those who have served the Church, who have labored in the care of souls, and who are distinguished for their learning and the holiness of their lives.
Source: Quod Multum (Vatican.va)