There are times in the life of a priest where he is forced to reflect on the essentials of his priesthood. This happened many times in past ages of persecution, for example when priests were hunted down in England and Ireland several centuries ago, or more recently under Communist oppression in various nations over the last century. The priest is then compelled to look to the heart of the matter, to "what matters" in his life, why he is who he is, and he discovers once again that it all comes down to the Mass.

For this he was ordained a priest of Jesus Christ, above all else to "do this". He was ordained to obey a command from the lips of Jesus of Nazareth, given in an upper room at a Jewish ritual meal two thousand years ago: "Do this in memory of me."

The Council of Trent teaches us that by those words at the Last Supper Jesus Christ ordained his disciples as priests of the New Covenant. Scriptural scholarship (not the mere dissection of texts, but scholarship that reverences the mind and culture of Israel) endorses the inspired teaching of the Fathers at Trent. Jesus instituted his new priesthood for his new covenant by a word of command. But this requires some explanation.

When God "speaks" in the Scriptures, something happens. When God commands, a new reality is created. When God utters his word, reality is changed. He spoke the word: "Let there be light!" and there was light, the massive blaze of the creation of the universe. He spoke his Ten Words, binding his People to a moral code, the ten commandments. But God offered them his help to live his law. In Jesus, God said "Go, teach and baptise…" and the apostles of Jesus were empowered to go out, to teach and baptize, and behold a new creation, the community of the Church expanding around our planet.

He said "Do this in memory of me…" and his friends at the supper table of the Passover henceforth can take bread and wine and something radically new always happens. As they obey him and "do this", it is truly and substantially changed into the Body and Blood of the One who commanded, the One who at the same time called and empowered them by his word.

It is all a matter of grace. It is all a matter of God passing on the authority granted to Jesus his beloved Son, his exousia, to use the Greek term used in the Gospels. This word of command and the grace to obey should enliven our hearts, for example when we hear our Lord say, "Love one another as I have loved you." or "Be perfect!" Without the corresponding gift to fulfil Christ's commands, these words sound very discouraging. We are but weak humans, so how can we be perfect? We find it hard to "love one another". Yet we are empowered by the God who sends his Spirit to dwell in our hearts, whose grace is perfected in our weakness. In that grace we have confidence and through that grace we discover our dignity as human persons.

It is all a matter of the transforming quality of the seven sacraments. Sacraments are moments that change people. They have the quality of being new beginnings, points for transformation, conversion. Three sacraments actually change us for ever. Laity and priests alike, have been permanently consecrated (set apart) by their Baptism and Confirmation and priests have received a third permanent consecration of Holy Orders. In different ways, we are all raised up into the realm of grace. For ever we have been baptized, chrismed and ordained. The "indelible character" that imprints the seal and image of Jesus on each of us in these sacraments, gives us our "place" in the worshipping Church.

A dynamic hierarchy of worship makes up the eternal liturgy of the whole Body of Christ, the Church. This is the work of Jesus our Great High Priest, offering himself in and through his Church to the Father in the union of the Holy Spirit. "Through him, with him, in him…" At the end of the eucharistic prayer, the priest raises the Host and Chalice together, and the self-giving or oblation of the whole Church is represented, taken up into the sacrificial self-giving love of the Blessed Trinity. The who assembly responds with the great "Amen!", the resounding "Yes!" of the faith of a priestly people.

The one leading or presiding over every celebration of the Eucharist is called a "priest". This word "priest" means one who offers sacrifice. Logically that suggest that the Eucharist or Mass is a sacrifice. The Church teaches that it is not merely "a" sacrifice, rather it is "the" One Sacrifice of Jesus, the same sacrifice he offered once and for all on the Cross. To put this another way, the Mass is the Sacrifice as the Cross in a sacramental form. What people saw then in terms of blood, death and suffering, we see in terms of a noble action of priest, bread, wine, prayer, people eating and drinking.

But what does it really mean to say that the Mass is the same Sacrifice as the Cross? To unpack this mystery, we must first ask: "What was happening on Calvary hill when Jesus was crucified?" It was the greatest revelation of God the Trinity on earth. How do we know this?

On a Cross, on an execution hill near the walls of Jerusalem, people saw a good young rabbi being executed by the Romans. But he was really God in human flesh, the Son, giving himself up to his Father, in and through the binding love of the Holy Spirit. On the Cross, in Jesus crucified, we get a glimpse into the Trinity: the self-giving eternal love of Father, Son and Spirit.

Is that then what we enter, what we are taken into, in every celebration of the Mass? Yes indeed, and that is the marvel, mystery and wonder of the Mass and the sacrament of the Eucharist. But, as Jesus commanded at the Last Supper, the Mass can only happen through human beings, through an ordained priesthood, through a "new covenant" priesthood. This sacrificing priesthood depends on and is drawn from the ranks of a new priestly People of God, "a nation of kings and priests", the new Israel which we call "the Church".

How clear it all was to those at the supper table with Jesus our Lord. They may not have fathomed what exactly was happening to them at that moment, for the Lord "had not yet risen from the dead". But they would have understood within their Hebrew religious culture the words Jesus used , words speaking of sacrifice, victimhood and priesthood, words related to the great Temple in Jerusalem. Later generations who fell away from Catholic eucharistic faith just over four centuries ago lacked those finely tuned ears. They failed to capture the meaning of the action of the Last Supper in Jewish terms which the Church has faithfully passed on.

To the disciples at the supper table it was all a matter of an amazing new sacrifice. Let us reflect in their terms on what the sacred eucharistic words of Jesus mean as recorded in various forms, first in 1 Corinthians 11: 23-25 and the Last Supper accounts in the Gospels of Mark, Matthew and Luke.

These disciples are commanded to "take and eat" this, "my body", and to drink this, "my blood". Their Master describes himself in the state of victimhood; the life force, the blood, is separated from the flesh, as was the case in temple sacrifices. His blood is poured out and his body is "given up for you". Note the words here, very carefully. His body and blood is not given primarily "to you" but first offered up, or handed over, in sacrifice "for you".

That is the language of sacrifice. This is what he is doing, making himself a victim for others. At the same time, intentionally he is offering himself as the priest. Then come the defining words, "the blood of the new and eternal covenant that will be shed for you and for the many", a sacrifice of expiation, redemption, propitiation for sins, "for the remission of sins" of the multitude, but binding the faithful to covenant relationship with God.

As devout Jews, they would have had a problem with the idea of drinking his blood. The blood as the life force belonged to God alone and could not be consumed, as is the Kosher law today. Here we see a radical development beyond the Old Covenant and into the New. But they would learn that eating his body and drinking his blood was to unite them to his life force, to become dependent on his life, to gain a supernatural life that is stronger than death, as Jesus himself explained in John chapter 6.

Finally from the lips of Jesus comes the divine command "Do this in memory of me". Again the Jewish ears would hear the empowering word of divine command linked to a new Passover. Note that his last meal with them was a holy Passover meal. That was no accident. He timed the meal and his own death to coincide with the Passover, the memorial action that recalled the liberation of the Jews from Egypt led by Moses. But Jesus gives his disciples the power to carry out a new great memorial action, not with the roasted lamb and unleavened bread of the old Passover meal, but with the new bread and grape wine of his eternal kingdom and covenant. This simple basic food is now changed into the living victim and priest of the one perfect Sacrifice that replaces a multitude of imperfect Temple sacrifices, a new sacrifice-meal to replace the sacrifice-meal of the Passover.

"Do this in memory of me." This is the great memorial, anamnesis in Greek, that is, a re-presentation or "replay" in modern English. It is not remembering in the head, "a memory", still less is it like a memorial plaque on a wall, rather it is a vital re-presentation or re-enactment that makes the great event from the past become present among us now, like a replay. The Jews had, and still have, a sense of this when celebrating the Passover meal. Hence we can sense why the Mass literally makes Calvary and Easter present here among us at this altar. It is the great "replay" bringing the Cross into our times, applying the power of the Cross as prayer for the living and the dead.

Nor would the Jewish mind find any problem reconciling a holy meal with a holy sacrifice. In the great Temple there were communion sacrifices where parts of the victim were cooked and then shared as holy food by the priest and those offering the gift. Such a sacred banquet joined them to the Holy God of Israel and to one another in covenant unity, in a sacred communion. Thus it is through the sacrament of the Eucharist, a Holy Communion, that we share most fully in the Sacrifice of the Lord, the Sacrifice of his Church. This is communion with God and communion with one another as "one bread, one body".

However, in light of the way Jesus adapted existing rituals, and in what he taught and did, his first priests of had to forget a merely cultic idea of priesthood, as if priesthood were just the function of carrying out external ritual acts in a temple: killing animals, sprinkling blood etc. At the Last Supper Jesus revealed his priesthood not only as some rituals but as service. When he knelt to wash the feet of fishermen he gave them a ministerial priesthood, that is, priesthood as service of others.

Yet the Eucharist is always the great source of this service, the source of spiritual energy to keep serving others. Those being ordained to offer this One Sacrifice are reminded by the bishop that they are called to model their lives on the self-giving love of Christ, victim and servant. He came "not to be served but to serve". Priests are called to make an acceptable sacrifice of their lives, day by day placing themselves, as it were, on the paten and in the chalice of self-sacrifice, as they pray with and for the people they are ordained to serve. They are called to heal, to reconcile with pardon and peace. Yet the source of their ministry of reconciliation is also the Eucharist, for the Eucharist is the same sacrifice as the Cross, and that was the greatest act of reconciliation between God and humanity in all history.

Therefore the priests of Jesus Christ take upon themselves his role of Suffering Servant, his selfless care as the Good Shepherd who knows and loves all his sheep. As they act in the Person of Christ, as an alter Christus, (another Christ) priests are called to identify, as Jesus did, with their people in times of anguish and pain, loneliness and sorrow. They are called to be prepared to witness to Jesus even unto death, just as we see in lands where priests and people together face persecution.

Having taken this journey into the priestly mysteries instituted by Our Lord at the Last Supper, all that remains is for priests is to strive to be obedient and faithful to the great trust they have received from the Lord. As we are all drawn into the mystery and the glory of his eucharistic words at the supper table, let us never forget his other quieter words recorded in Saint John's account of the Last Supper, word that may be sung after Communion at an ordination Mass: "I will not now call you servants….But I have called you friends…You are my friends if you do the things that I command you."