In Revelation 5:1-10, St. John describes a seven-sealed scroll that no one could open:

And I saw in the right hand of him who was seated on the throne a scroll written within and on the back, sealed with seven seals; and I saw a strong angel proclaiming with a loud voice, “Who is worthy to open the scroll and break its seals?” And no one in heaven or on earth or under the earth was able to open the scroll or to look into it, and I wept much that no one was found worthy to open the scroll or to look into it.

An elder calms John down, saying, “Weep not; lo, the Lion of the tribe of Judah, the Root of David, has conquered, so that he can open the scroll and its seven seals.” And it’s here that John sees Christ, “between the throne and the four living creatures and among the elders.” The context here is deeply liturgical: the four living creatures represent the four Gospels (Rev. 4:6-7), and Christ is surrounded by the elders (presbyters, or priests). Jesus Christ is presented in an almost-paradoxical Eucharistic way: “I saw a Lamb standing, as though it had been slain.” And it’s Christ, presented in this way, that is the key to unlocking the seven seals, and revealing the meaning of the scroll. This is true for virtually every aspect of the Christian life. Here are seven other areas in which the Eucharist is the “key” to opening up a fuller understanding.

I. The Key to the New Covenant

In theological circles, a lot is said about “covenantal theology,” and Christianity is often referred to as “the New Covenant.” Given this, it’s striking that Christ specifically mentions the New Covenant exactly once in the New Testament, and it’s at the Last Supper. As He is consecrating the wine into His Blood, He says, “This cup is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me” (1 Corinthians 11:25; Matthew 26:28; Mark 14:24; Luke 22:20). So Christ is telling us, if you want to understand the New Covenant, you need to look here:

If you’ve got a covenantal theology that isn’t centered around the Eucharist, you’re not getting the full picture.

II. The Key to the Old Covenant

The Old Covenant can be a bit baffling to modern readers: what’s with all of the animal sacrifice and bloodshed? Hebrews 9:18-22 explains:

Hence even the first covenant was not ratified without blood. For when every commandment of the law had been declared by Moses to all the people, he took the blood of calves and goats, with water and scarlet wool and hyssop, and sprinkled both the book itself and all the people, saying, “This is the blood of the covenant which God commanded you.” And in the same way he sprinkled with the blood both the tent and all the vessels used in worship. Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins.

Listen to how Christ’s words echo, across time and space, in Moses’. And if you go back to the Old Testament passage that Hebrews is referencing, this connection is even more profound (Exodus 24:7-11):

Then he [Moses] took the book of the covenant, and read it in the hearing of the people; and they said, “All that the Lord has spoken we will do, and we will be obedient.” And Moses took the blood and threw it upon the people, and said, “Behold the blood of the covenant which the Lord has made with you in accordance with all these words.” Then Moses and Aaron, Nadab, and Abi′hu, and seventy of the elders of Israel went up, and they saw the God of Israel; and there was under his feet as it were a pavement of sapphire stone, like the very heaven for clearness. And he did not lay his hand on the chief men of the people of Israel; they beheld God, and ate and drank.

The entire passage proceeds liturgically. It begins wiht Scriptural readings, from the book of the covenant. The people then respond with a Creed of sorts, their profession of faith. Then Moses declares the blood of the covenant, parallel to the consecration of the Eucharist. And then it’s time for a Heavenly communion: Moses and the elders behold God, eat and drink.

There’s a principle to bear in mind here: the Old Covenant prefigurements are always inferior to the New Covenant fulfillments. The foreshadowing is never as awesome as the thing being foreshadowed. So the Liturgy that Exodus 24 is prefiguring is more amazing than eating and drinking while seeing the God of Israel.

As it turns out, this is just one of several places in which the Old Testament points us towards the Eucharist. I’ve written on this before, so I’ll just point to a few of the more obvious ones.

The manna in the desert (Exodus 16) points to the Body of Christ. Jesus makes this connection in John 6, in which He claims to be superior to the manna (John 6:49-50), and says, “I am the living bread which came down from heaven; if any one eats of this bread, he will live for ever; and the bread which I shall give for the life of the world is my flesh.” The Our Father, in calling for our “daily bread,” references Christ in this capacity, as our supersubstantial Manna from Heaven.

(Exodus 16) points to the Body of Christ. Jesus makes this connection in John 6, in which He claims to be superior to the manna (John 6:49-50), and says, “I am the living bread which came down from heaven; if any one eats of this bread, he will live for ever; and the bread which I shall give for the life of the world is my flesh.” The Our Father, in calling for our “daily bread,” references Christ in this capacity, as our supersubstantial Manna from Heaven. The water from the rock (Exodus 17) points to the Blood of Christ: St. Paul connects the manna and the water in 1 Corinthians, referring to them as the Jews’ supernatural food and drink (1 Cor. 10:3-4).

(Exodus 17) points to the Blood of Christ: St. Paul connects the manna and the water in 1 Corinthians, referring to them as the Jews’ supernatural food and drink (1 Cor. 10:3-4). The Passover (Exodus 12) points to the Eucharist in perhaps the most obvious way. 1 Corinthians 5:7 describes Christ as “our Paschal Lamb,” who has “been sacrificed.” This sacrifice is inseparable from the Sacrifice of the Mass, instituted at the Last Supper — which, not coincidentally, takes place on Passover (Luke 22:15). Also, the Eucharistic discourse in John 6, referenced above? It takes place at Passover time, as well (John 6:4).

There are several other examples, but as I said, I’ve written on that elsewhere. For now, it suffices to say that you can’t full understand any of the Old Testament passages, or the point of the bloody sacrificial system more broadly, without understanding the Eucharistic Sacrifice.

III. The Key to the Mass

In 1 Corinthians 10, St. Paul draws a three-fold parallel, between the sacrifical systems of the pagans, the Jews, and the Christians (1 Cor. 10:16-22):

The cup of blessing which we bless, is it not a participation in the blood of Christ? The bread which we break, is it not a participation in the body of Christ? Because there is one bread, we who are many are one body, for we all partake of the one bread. Consider the practice of Israel; are not those who eat the sacrifices partners in the altar? What do I imply then? That food offered to idols is anything, or that an idol is anything? No, I imply that what pagans sacrifice they offer to demons and not to God. I do not want you to be partners with demons. You cannot drink the cup of the Lord and the cup of demons. You cannot partake of the table of the Lord and the table of demons. Shall we provoke the Lord to jealousy? Are we stronger than he?

Start with the pagans. They have sacrifices to demons, at the altar, which Paul describes as “the table of demons.” They then eat and drink these sacrifices. Paul describes their sacrificial libation as “the cup of demons.” In eating the sacrifice, they become “partners with demons.”

Compare this with the Jews of Israel. Their priests also sacrifice at the altar, but to God, rather than to demons. And as Paul notes, the people participate in the sacrifice by eating it: “are not those who eat the sacrifices partners in the altar?”

Now look at Christianity. Our priests also sacrifice at the altar, which Paul describes as “the table of the Lord.” We then eat and drink these sacrifices. Paul describes the Blood of Christ, our sacrificial libation, as “the Cup of the Lord,” and — in a nod to the Passover, as “the Cup of Blessing.” And it’s in eating and drinking this Eucharistic Sacrifice that we participate in Christ’s Body and Blood, and in His Sacrifice. If you don’t have these sacrificial, Eucharistic elements in your understanding of Christianity, this whole parallel breaks down. This is why the Catechism can say that

The Eucharist is “the source and summit of the Christian life.” “The other sacraments, and indeed all ecclesiastical ministries and works of the apostolate, are bound up with the Eucharist and are oriented toward it. For in the blessed Eucharist is contained the whole spiritual good of the Church, namely Christ himself, our Pasch.”

This is central to understanding the Mass and the Divine Liturgy and any of the early Christian liturgies. For example, the Liturgy of St. James is believed to be the oldest continually-used Liturgy. The Cherubic Hymn, a part of the Liturgy that was probably present from the early 300s, beautifully expresses this centrality of the Eucharist:

Let all mortal flesh be silent, and stand with fear and trembling, and meditate nothing earthly within itself:— For the King of kings and Lord of lords, Christ our God, comes forward to be sacrificed, and to be given for food to the faithful; and the bands of angels go before Him with every power and dominion, the many-eyed cherubim, and the six-winged seraphim, covering their faces, and crying aloud the hymn, Alleluia, Alleluia, Alleluia.

It’s painting a picture of the Divine Liturgy as an earthly manifestation of the Heavenly Liturgy we see laid out in the Book of Revelation. And at the heart of this Liturgy, is Christ’s self-offering, given to us in the Eucharist. And it’s this that explains the paradox of the Lamb standing as though slain. We don’t expect a slain lamb to be standing: we expect it to be lying down, dead and defeated. But Christ’s self-Sacrifice is His victory, not His defeat: “and I, when I am lifted up from the earth, will draw all men to myself” (John 12:32). He isn’t just the victim: He’s also the priest. At the Heavenly banquet, He is both host and Host. St. John Chrysostom captures this Heavenly dimension, in On the Priesthood (c. 387 A.D.):

For when you see the Lord sacrificed, and laid upon the altar, and the priest standing and praying over the victim, and all the worshippers empurpled with that precious blood, can you then think that you are still among men, and standing upon the earth? Are you not, on the contrary, straightway translated to Heaven, and casting out every carnal thought from the soul, do you not with disembodied spirit and pure reason contemplate the things which are in Heaven? Oh! What a marvel! What love of God to man! He who sits on high with the Father is at that hour held in the hands of all, and gives Himself to those who are willing to embrace and grasp Him. And this all do through the eyes of faith! Do these things seem to you fit to be despised, or such as to make it possible for any one to be uplifted against them?

IV. Key to Early Christianity

The Eucharist wasn’t just key to the Liturgy of the early Christians, it was key to their entire lives, and to their Church. We see this extremely early on. St. Ignatius of Antioch, a student of the Apostle John’s, writing c. 107 A.D., uses the Gnostics’ denial of the Real Presence as proof that they didn’t belong in the Church:

They [the Gnostics] abstain from the Eucharist and from prayer, because they confess not the Eucharist to be the flesh of our Saviour Jesus Christ, which suffered for our sins, and which the Father, of His goodness, raised up again. Those, therefore, who speak against this gift of God, incur death in the midst of their disputes. But it were better for them to treat it with respect, that they also might rise again. It is fitting, therefore, that ye should keep aloof from such persons, and not to speak of them either in private or in public, but to give heed to the prophets, and above all, to the Gospel, in which the passion [of Christ] has been revealed to us, and the resurrection has been fully proved. But avoid all divisions, as the beginning of evils.

Ignatius isn’t trying to convince his readers that the Eucharist really is the Flesh and Blood of Jesus Christ. He knows that they know that. Instead, he’s telling the Church that, since the Gnostics don’t affirm this belief, we can’t be in communion with them. He also describes their denial of the Eucharist as a cause of their spiritual death, and says it would be better if they repented, that they might rise again.

In 180 A.D., we see St. Irenaeus of Lyons make a very similar argument. (By way of reference, the first recorded use of “Trinity” to describe the Godhead is 181 A.D., so we’re still talking quite early in Christian history). Irenaeus is responding to those who deny the bodily resurrection of Christians at the end of time. He disproves their view, by showing that it’s incompatible with the Real Presence of the Eucharist:

Then, again, how can they say that the flesh, which is nourished with the body of the Lord and with His blood, goes to corruption, and does not partake of life? Let them, therefore, either alter their opinion, or cease from offering the things just mentioned. But our opinion is in accordance with the Eucharist, and the Eucharist in turn establishes our opinion. For we offer to Him His own, announcing consistently the fellowship and union of the flesh and Spirit. For as the bread, which is produced from the earth, when it receives the invocation of God, is no longer common bread, but the Eucharist, consisting of two realities, earthly and heavenly; so also our bodies, when they receive the Eucharist, are no longer corruptible, having the hope of the resurrection to eternity.

In other words, the Eucharist is a communion with Jesus Christ, Body, Blood, Soul, and Divinity. And we commune with Him both spiritually and physically. Because our bodies receive the God-Man Jesus Christ, we can be assured that our bodies won’t be simply discarded at the end of our lives. Rather, as Christ says, “he who eats my flesh and drinks my blood has eternal life, and I will raise him up at the last day” (John 6:54). What’s striking is that Irenaeus’ belief in the General Resurrection is, by his own admission, rooted in his belief in the Real Presence. It’s the heart of his theology, and it’s the key to understanding the beliefs of the early Christians.

To see what happens when someone doesn’t have this key, look to Minucius Felix’s Octavius (written c. 150-270 A.D.) Here, we find a Roman objection to Christianity rooted in a bizarre misunderstanding of the Eucharist:

Now the story about the initiation of young novices is as much to be detested as it is well known. An infant covered over with meal, that it may deceive the unwary, is placed before him who is to be stained with their rites: this infant is slain by the young pupil, who has been urged on as if to harmless blows on the surface of the meal, with dark and secret wounds. Thirstily – O horror! they lick up its blood; eagerly they divide its limbs. By this victim they are pledged together; with this consciousness of wickedness they are covenanted to mutual silence.

The Romans are well aware that the Christ child is central to Christianity, and that there’s something about eating flesh and blood under the appearances of bread. But they’ve (intentionally or mistakenly) misunderstood it in the most barbaric, cannibalistic way imaginable. If your Christianity isn’t capable of being misunderstood in this way, it’s not the same faith practiced by the early Christians.

V. The Key to the Church

Returning to 1 Corinthians 10, recall how St. Paul says, “Because there is one bread, we who are many are one body, for we all partake of the one bread” (1 Cor. 10:17). The order of causality is important there. Sometimes, people think that we have Communion to celebrate the fact that we’re one. Because we’re one, we share the same Eucharist. But no, St. Paul says the opposite: because we share the same Eucharist, we are one Body. In this view, our union as Church isn’t just celebrated by the Eucharist; in a very real way, it’s caused by the Eucharist.

Our ecclesial communion is rooted in Sacramental Communion. The Mystical Body of Christ, the Church (Ephesians 5:23) is grounded in the Sacramental Body of Christ, the Eucharist. Indeed, this is why the Church is called the Mystical Body of Christ: it’s rooted in the great sacramental Mystery. Keep that in mind when you encounter Scriptures like “Christ loved the church and gave himself up for her, that he might sanctify her, having cleansed her by the washing of water with the word, that he might present the church to himself in splendor, without spot or wrinkle or any such thing, that she might be holy and without blemish” (Ephesians 5:25-27). The Church at the heart of the mystery of salvation is rooted in the Eucharist.

VI. Key to the Lives of the Saints

There are a few senses in which we can see the centrality of the Eucharist for the lives of the Saints. The most obvious examples are those Christians who put their lives on the line to preserve the Blessed Sacrament. St. Ambrose (340-397) tells the story of his late brother Satyrus, who risked drowning to protect the Eucharist after a shipwreck:

He, before being initiated in the more perfect mysteries, being in danger of shipwreck when the ship that bore him, dashed upon rocky shallows, was being broken up by the waves tossing it hither and there, fearing not death but lest he should depart this life without the Mystery, asked of those whom he knew to be initiated the divine Sacrament of the faithful; not that he might gaze on secret things with curious eyes, but to obtain aid for his faith. For he caused it to be bound in a napkin, and the napkin round his neck, and so cast himself into the sea, not seeking a plank loosened from the framework of the ship, by floating on which he might be rescued, for he sought the means of faith alone. And so believing that he was sufficiently protected and defended by this, he sought no other aid.

Or take the example of Tarcisius, a twelve year-old boy from the third century. He was an acolyte, and was carrying the Eucharist to the sick, when he was harassed by a group of pagan boys. When he refused to give them the Sacrament, they beat him to death. A poem commemorating him, written by Pope Damasus I, recalls that “When an insane gang pressed saintly Tarsicius, who was carrying the sacraments of Christ, to display them to the profane, he preferred to be killed and give up his life rather than betray to rabid dogs the heavenly body.”

But there are other Saints, perhaps less obvious, whose very lives become Eucharistic, leading them to pour themselves out. You’ve got St. Paul, who says, “Even if I am to be poured as a libation upon the sacrificial offering of your faith, I am glad and rejoice with you all” (Philippians 2:17), and “For I am already on the point of being sacrificed; the time of my departure has come” (2 Timothy 4:6). Literally, that second passage reads, “I am already on the point of being poured out in sacrifice.” Compare these declarations to the words of Jesus Christ at the Last Supper, “This is My Blood of the New Covenant, which is poured out for many” (Mark 14:24). Likewise, St. Ignatius, writing to the Romans en route to being martyred there, says, “I am the wheat of God, and let me be ground by the teeth of the wild beasts, that I may be found the pure bread of Christ.”

St. Augustine views St. Lawrence the same way:

The Roman Church commends this day to us as the blessed Laurence’s day of triumph, on which he trod down the world as it roared and raged against him; spurned it as it coaxed and wheedled him; and in each case, conquered the devil as he persecuted him. For in that Church, you see, as you have regularly been told, he performed the office of deacon; it was there that he administered the sacred chalice of Christ’s blood; there that he shed his own blood for the name of Christ. The blessed apostle John clearly explained the mystery of the Lord’s supper when he said Just as Christ laid down his life for us, so we too ought to lay down our lives for the brethren. St Laurence understood this, my brethren, and he did it; and he undoubtedly prepared things similar to what he received at that table. He loved Christ in his life, he imitated him in his death.

VII. The Key to Your Own Spiritual Life

Each of the Eucharistic Saints I mentioned in the last section risked their lives for the Blessed Sacrament. But in his sermon on St. Lawrence, Augustine is quick to note that “not only the roses of martyrs but also the lilies of virgins, and the ivy of married people, and the violets of widows. There is absolutely no kind of human beings, my dearly beloved, who need to despair of their vocation; Christ suffered for all.”

And Mother Teresa’s advice to priests is applicable, in a broader sense, to all of us:

By your life woven with the Eucharist, God’s love in Jesus, hidden under the humble appearances of bread and wine, can be lived in all its greatness and beauty in the humble events of daily life. You must continue your Mass after its daily celebration during the Liturgy, by your sincere fidelity to the little moment-to-moment things of life. Like the drops of oil that feed the sanctuary lamp which burns continually near the living Jesus in the tabernacle, your life must continue as a living extension of the Eucharist that you offer. With this Bread you must be broken for many, with this Cup your life must be poured out. Charity is love in action.

St. Josemaria gives some concrete advice for keeping the Eucharist at the center of our lives: to spend time, both inside and outside of Mass, in front of the Blessed Sacrament:

I cannot see how anyone could live as a Christian and not feel the need for the constant friendship of Jesus in the word and in the bread, in prayer and in the Eucharist. And I easily understand the ways in which successive generations of faithful have expressed their love for the Eucharist, both with public devotions making profession of the faith and with silent, simple practices in the peace of a church or the intimacy of their hearts. The important thing is that we should love the Mass and make it the centre of our day. If we attend Mass well, surely we are likely to think about our Lord during the rest of the day, wanting to be always in his presence, ready to work as he worked and love as he loved. And so we learn to thank our Lord for his kindness in not limiting his presence to the time of the sacrifice of the altar. He has decided to stay with us in the host which is reserved in the tabernacle. For me the tabernacle has always been a Bethany, a quiet and pleasant place where Christ resides. A place where we can tell him about our worries, our sufferings, our desires, our joys, with the same sort of simplicity and naturalness as Martha, Mary and Lazarus. That is why I rejoice when I stumble upon a church in town or in the country; it’s another tabernacle, another opportunity for the soul to escape and join in intention our Lord in the Sacrament.

This is the Eucharistic faith proclaimed by Christ, by the Old and New Testament, by the Saints, by the Divine Liturgy, and by the Church throughout the ages. Getting the most out of Christianity requires a deep understanding of this Mystery.