13 Priests who perform their duties sincerely and indefatigably in the Spirit of Christ arrive at holiness by this very fact. Since they are ministers of God's word, each day they read and hear the word of God, which it is their task to teach others. If at the same time they are ready to receive the word themselves they will grow daily into more perfect followers of the Lord. As St. Paul wrote to Timothy, "Let this be thy study, these thy employments, so that all may see how well thou doest. Two things claim thy attention, thyself and the teaching of the faith, spend thy care on them; so wilt thou and those who listen to thee achieve salvation" (1 Tim 4:15-16). As they seek how they may better teach others what they have learned, they will better understand "the unfathomable riches of Christ" (Eph 3:8) and the manifold wisdom of God. If they keep in mind that it is God who opens hearts, and that power comes not from themselves but from the might of God, in the very fact of teaching God's word they will be brought closer to Christ the Teacher and led by his Spirit. Thus those who commune with Christ share in God's love, the mystery of which, kept hidden from the beginning of time, is revealed in Christ. Priests act especially in the person of Christ as ministers of holy things, particularly in the Sacrifice of the Mass, the sacrifice of Christ who gave himself for the sanctification of men. Hence, they are asked to take example from that with which they deal, and inasmuch as they celebrate the mystery of the Lord's death they should keep their bodies free of wantonness and lusts. In the mystery of the Eucharistic Sacrifice, in which priests fulfill their greatest task, the work of our redemption is being constantly carried on; and hence the daily celebration of Mass is strongly urged, since even if there cannot be present a number of the faithful, it is still an act of Christ and of the Church. Thus when priests join in the act of Christ the Priest, they offer themselves entirely to God, and when they are nourished with the body of Christ they profoundly share in the love of him who gives himself as food to the faithful. In like fashion they are united with the intention and love of Christ when they administer the sacraments. This is true in a special way when in the performance of their duty in the sacrament of Penance they show themselves altogether and always ready whenever the sacrament is reasonably sought by the faithful. In the recitation of the Divine Office, they offer the voice of the Church which perseveres in prayer in the name of the whole human race, together with Christ who "lives on still to make intercession on our behalf." As they direct and nourish the People of God, may they be aroused by the example of the Good Shepherd that they may give their life for their sheep, ready for the supreme sacrifice following the example of priests who, even in our own day, have not shrunk from giving their lives. As they are leaders in the faith and as they "enter the sanctuary with confidence, through the blood of Christ" (Heb 10:19) they approach God "with sincere hearts in the full assurance of the faith" (Heb 10:22) they set up a sure hope for their faithful, that they may comfort those who are depressed by the same consolation wherewith God consoles them. As leaders of the community they cultivate an asceticism becoming to a shepherd of souls, renouncing their personal convenience, seeking not what is useful to themselves but to many, for their salvation, always making further progress to do their pastoral work better and, where needful, prepared to enter into new pastoral ways under the direction of the Spirit of Love, which breathes where it will.
Source: Presbyterorum Ordinis (Vatican.va)