Encyclical Letter on the Holy Eucharist - Parts 28 & 29

28. Lastly, the Church is apostolic in the sense that she “continues to be taught, sanctified and guided by the Apostles until Christ's return, through their successors in pastoral office: the college of Bishops assisted by priests, in union with the Successor of Peter, the Church's supreme pastor”.⁵³ Succession to the Apostles in the pastoral mission necessarily entails the sacrament of Holy Orders, that is, the uninterrupted sequence, from the very beginning, of valid episcopal ordinations.⁵⁴ This succession is essential for the Church to exist in a proper and full sense. 

The Eucharist also expresses this sense of apostolicity. As the Second Vatican Council teaches, “the faithful join in the offering of the Eucharist by virtue of their royal priesthood”,⁵⁵ yet it is the ordained priest who, “acting in the person of Christ, brings about the Eucharistic Sacrifice and offers it to God in the name of all the people”.⁵⁶ For this reason, the Roman Missal prescribes that only the priest should recite the Eucharistic Prayer, while the people participate in faith and in silence.⁵⁷

29. The expression repeatedly employed by the Second Vatican Council, according to which “the ministerial priest, acting in the person of Christ, brings about the Eucharistic Sacrifice”,⁵⁸ was already firmly rooted in papal teaching.⁵⁹ As I have pointed out on other occasions, the phrase in persona Christi “means more than offering 'in the name of' or 'in the place of' Christ. In persona means in specific sacramental identification with the eternal High Priest who is the author and principal subject of this sacrifice of his, a sacrifice in which, in truth, nobody can take his place”.⁶⁰ The ministry of priests who have received the sacrament of Holy Orders, in the economy of salvation chosen by Christ, makes clear that the Eucharist which they celebrate is a gift which radically transcends the power of the assembly and is in any event essential for validly linking the Eucharistic consecration to the sacrifice of the Cross and to the Last Supper. The assembly gathered together for the celebration of the Eucharist, if it is to be a truly Eucharistic assembly, absolutely requires the presence of an ordained priest as its president. On the other hand, the community is by itself incapable of providing an ordained minister. This minister is a gift which the assembly receives through episcopal succession going back to the Apostles. It is the Bishop who, through the Sacrament of Holy Orders, makes a new presbyter by conferring upon him the power to consecrate the Eucharist. Consequently, “the Eucharistic mystery cannot be celebrated in any community except by an ordained priest, as the Fourth Lateran Council expressly taught”.⁶¹ 

The Holy Eucharist Unites Heaven and Earth...

Taken from the Encyclical on the Holy Eucharist - Pope John Paul II

When I think of the Eucharist, and look at my life as a priest, as a Bishop and as the Successor of Peter, I naturally recall the many times and places in which I was able to celebrate it. I remember the parish church of Niegowiæ, where I had my first pastoral assignment, the collegiate church of Saint Florian in Krakow, Wawel Cathedral, Saint Peter's Basilica and so many basilicas and churches in Rome and throughout the world. I have been able to celebrate Holy Mass in chapels built along mountain paths, on lakeshores and seacoasts; I have celebrated it on altars built in stadiums and in city squares... This varied scenario of celebrations of the Eucharist has given me a powerful experience of its universal and, so to speak, cosmic character. Yes, cosmic!

Because even when it is celebrated on the humble altar of a country church, the Eucharist is always in some way celebrated on the altar of the world. It unites heaven and earth. It embraces and permeates all creation. The Son of God became man in order to restore all creation, in one supreme act of praise, to the One who made it from nothing. He, the Eternal High Priest who by the blood of His Cross entered the eternal sanctuary, thus gives back to the Creator and Father all creation redeemed. He does so through the priestly ministry of the Church, to the glory of the Most Holy Trinity. Truly this is the mysterium fidei which is accomplished in the Eucharist: the world which came forth from the hands of God the Creator now returns to Him redeemed by Christ.