Priests by sacred ordination and mission which they receive from the bishops are promoted to the service of Christ the Teacher, Priest and King.
Priests, who are taken from among men and ordained for men in the things that belong to God in order to offer gifts and sacrifices for sins, nevertheless live on earth with other men as brothers. The Lord Jesus, the Son of God, a Man sent by the Father to men, dwelt among us and willed to become like his brethren in all things except sin. The holy apostles imitated him. Blessed Paul, the doctor of the Gentiles, "set apart for the Gospel of God" (Rom 1:1) declares that he became all things to all men that he might save all. Priests of the New Testament, by their vocation and ordination, are in a certain sense set apart in the bosom of the People of God. However, they are not to be separated from the People of God or from any person; but they are to be totally dedicated to the work for which the Lord has chosen them.
They cannot be ministers of Christ unless they be witnesses and dispensers of a life other than earthly life. But they cannot be of service to men if they remain strangers to the life and conditions of men. Their ministry itself, by a special title, forbids that they be conformed to this world; yet at the same time it requires that they live in this world among men.
Since no one can be saved who does not first believe, priests, as co-workers with their bishops, have the primary duty of proclaiming the Gospel of God to all. In this way they fulfill the command of the Lord: "Going therefore into the whole world preach the Gospel to every creature" (Mk 16:15), and they establish and build up the People of God. Through the saving word the spark of faith is lit in the hearts of unbelievers, and fed in the hearts of the faithful. Faith comes from hearing, and hearing through the word of Christ.
But priestly preaching is often very difficult in the circumstances of the modern world. In order that it might more effectively move men's minds, the word of God ought not to be explained in a general and abstract way, but rather by applying the lasting truth of the Gospel to the particular circumstances of life.
The ministry of the word is carried out in many ways, according to the various needs of those who hear and the special gifts of those who preach. In areas or communities of non-Christians, the proclaiming of the Gospel draws men to faith and to the sacraments of salvation. In the Christian community, especially among those who seem to understand and believe little of what they practice, the preaching of the word is needed for the very ministering of the sacraments. They are precisely sacraments of faith, a faith which is born of and nourished by the word. This is especially true of the Liturgy of the Word in the celebration of Mass, in which the proclaiming of the death and resurrection of Christ is inseparably joined to the response of the people who hear, and to the very offering whereby Christ ratified the New Testament in his blood.
The Eucharistic Action, over which the priest presides, is the very heart of the congregation. So priests must instruct their people to offer to God the Father the Divine Victim in the Sacrifice of the Mass, and to join to it the offering of their own lives. In the spirit of Christ the Shepherd, they must prompt their people to confess their sins with a contrite heart in the sacrament of Penance, so that, mindful of his words "Repent for the kingdom of God is at hand" (Mt 4:17), they are drawn closer to the Lord more and more each day. Priests likewise must instruct their people to participate in the celebrations of the sacred liturgy in such a way that they become proficient in genuine prayer. They must coax their people on to an ever more perfect and constant spirit of prayer for every grace and need. They must gently persuade everyone to the fulfillment of the duties of his state of life, and to greater progress in responding in a sensible way to the evangelical counsels. Finally, they must train the faithful to sing hymns and spiritual songs in their hearts to the Lord, always giving thanks to God the Father for all things in the name of our Lord Jesus Christ.
In building up of the Church, priests must treat all with exceptional kindness in imitation of the Lord. They should act toward men, not as seeking to please them, but in accord with the demands of Christian doctrine and life. They should teach them and admonish them as beloved sons, according to the words of the Apostle: "Be urgent in season, out of season, reprove, entreat, rebuke in all patience and doctrine" (2 Tim 4:2).
Priests therefore, as educators in the faith, must see to it either by themselves or through others that the faithful are led individually in the Holy Spirit to a development of their own vocation according to the Gospel, to a sincere and practical charity, and to that freedom with which Christ has made us free. Ceremonies however beautiful, or associations however flourishing, will be of little value if they are not directed toward the education of men to Christian maturity.
Although they have obligations toward all men, priests have a special obligation to the poor and weak entrusted to them, for our Lord himself showed that he was united to them, and their evangelization is mentioned as a sign of messianic activity.
The office of pastor is not confined to the care of the faithful as individuals, but also in a true sense is extended to the formation of a genuine Christian community. Yet the spirit of the community should be so fostered as to embrace not only the local church, but also the universal Church. The local community should promote not only the care of its own faithful, but, filled with a missionary zeal, it should prepare also the way to Christ for all men. In a special way, catechumens and the newly-baptized who must be educated gradually to know and to live the Christian life are entrusted to his care.
Priests, never losing sight of the fullness of the priesthood which the bishops enjoy, must respect in them the authority of Christ, the Supreme Shepherd. They must therefore stand by their bishops in sincere charity and obedience. This priestly obedience, imbued with a spirit of cooperation is based on the very sharing in the episcopal ministry which is conferred on priests both through the Sacrament of Orders and the canonical mission.
Priests have been placed in the midst of the laity to lead them to the unity of charity, "loving one another with fraternal love, eager to give one another precedence" (Rom 12:10). They are defenders of the common good, with which they are charged in the name of the bishop. At the same time, they are strenuous assertors of the truth, lest the faithful be carried about by every wind of doctrine
Priests should not be sent singly to a new field of labor, especially to one where they are not completely familiar with the language and customs; rather, after the example of the disciples of Christ, they should be sent two or three together so that they may be mutually helpful to one another.
Parents and teachers and all who are engaged in any way in the education of boys and young men should so prepare them that they will recognize the solicitude of our Lord for his flock, will consider the needs of the Church, and will be prepared to respond generously to our Lord when he calls, saying: "Here I am Lord, send me" (Is 6:8).
Holiness does much for priests in carrying on a fruitful ministry. Although divine grace could use unworthy ministers to effect the work of salvation, yet for the most part God chooses, to show forth his wonders, those who are more open to the power and direction of the Holy Spirit, and who can by reason of their close union with Christ and their holiness of life say with St. Paul: "And yet I am alive; or rather, not I; it is Christ that lives in me" (Gal 2:20).
Perfect and perpetual continence for the sake of the Kingdom of Heaven, commended by Christ the Lord and through the course of time as well as in our own days freely accepted and observed in a praiseworthy manner by many of the faithful, is held by the Church to be of great value in a special manner for the priestly life. Indeed, it is not demanded by the very nature of the priesthood, as is apparent from the practice of the early Church and from the traditions of the Eastern Churches. where, besides those who with all the bishops, by a gift of grace, choose to observe celibacy, there are also married priests of highest merit. It permanently exhorts all those who have received the priesthood and marriage to persevere in their holy vocation so that they may fully and generously continue to expend themselves for the sake of the flock commended to them.
Since the beginning, the ordained ministry has been conferred and exercised in three degrees: that of bishops, that of presbyters, and that of deacons.
The bishop receives the fullness of the sacrament of Holy Orders, which integrates him into the episcopal college and makes him the visible head of the particular Church entrusted to him. As successors of the apostles and members of the college, the bishops share in the apostolic responsibility and mission of the whole Church under the authority of the Pope, successor of St. Peter.
Priests are united with the bishops in sacerdotal dignity and at the same time depend on them in the exercise of their pastoral functions; they are called to be the bishops' prudent co-workers. They form around their bishop the presbyterium which bears responsibility with him for the particular Church. They receive from the bishop the charge of a parish community or a determinate ecclesial office.
Deacons are ministers ordained for tasks of service of the Church; they do not receive the ministerial priesthood, but ordination confers on them important functions in the ministry of the word, divine worship, pastoral governance, and the service of charity, tasks which they must carry out under the pastoral authority of their bishop.
The Church confers the sacrament of Holy Orders only on baptized men (viri). Church authority alone has the responsibility and right to call someone to receive the sacrament of Holy Orders.
The above article is a short summary of parts of the Catechism of the Catholic Church found at: http://www.vatican.va/archive/catechism/ccc_toc.htm. Due to space limitations, much was not included.