Part I: The Liturgy of the Word   

Introductory rites 

The Mass begins with a procession of, at minimum, the priest into the sanctuary. The priest and anyone who accompanies him represents the congregation, and their journey symbolizes the Christian journey through life to the heavenly courts. 

Oftentimes, at the front of the procession, one of the servers (a crucifer) carries a crucifix symbolizing that Jesus is our “leader to salvation” (Heb 2:10). 

The Mass then officially begins with the priest and people making the Sign of the Cross, a gesture that dates back to the first century of Christianity and summarizes the Christian belief in a Trinitarian God who descended from heaven to earth, who is now seated at the right hand of the Father, and whose death on a cross opened heaven’s gates. 

This is followed by a greeting. 

The priest may echo St. Paul’s words in 2 Corinthians 13:13, “The grace of Our Lord Jesus Christ, and the Love of God, and the Communion of the Holy Spirit be with you all.” 

Or, he can simply say, “The Lord be with you.” Either way, the people respond, “And with your Spirit,” acknowledging that the priest stands there in the person of Christ by the power of the Holy Spirit. 

Penitential rite 

Next, following the example of the tax collector in Luke 18:10-14, who Christ commended for approaching God by first crying out, “O Lord, have mercy on me a sinner,” Catholics acknowledge our sinfulness and ask God’s forgiveness. 

This can happen through the Kyrie — “Lord have mercy; Christ have mercy; Lord have mercy.” — an ancient penitential prayer with a petition for each of the Three Persons of the Trinity. 

It can also happen through the Confiteor, Latin for “I confess,” which calls us to admit we’ve sinned by our own free will (“through my fault, through my fault, through my most grievous fault”). 

Both expressions of contrition also call us to imitate the tax collector from Luke in another way, gently striking our breast in sorrow, demonstrating with actions as well as words, our remorse. 

A third option, less frequently used, is sprinkling, with the priest casting holy water upon the people as a reminder of our baptism. 

The Gloria 

Part of the Church’s liturgy since A.D. 128, the Gloria is the hymn of praise the angels sang at Christ’s birth, and that John heard in heaven (Lk 2:13-14, Rv 15:4). The hymn is a doxology, literally “word of praise,” a prayer expressing the Church’s great joy in God becoming man and revealing himself to us. 

After the Gloria, comes a brief opening prayer called the Collect. 

The readings 

When the Word of God is proclaimed from the pulpit, Christ is really and truly present to his people. This encounter with Christ in his Scriptures has, since the days of the apostles, occupied a central place in the liturgy, with Catholics seeking to heed St. Paul’s admonition that “Faith comes from what is heard” (Rom 10:17). 

Today, the first reading is drawn from the books of the Old Testament, the Scriptures of ancient Israel that tell of salvation history’s beginnings and point forward to the promised Savior. 

Next comes a selection from the Psalms. In ancient Israel, the Psalms were sung antiphonally, with a cantor singing a series of lines and the congregation responding with a repeated line. This is how Jesus and his mother prayed the Psalms, and this is how Catholics today continue to pray them. 

The second reading comes from the books of the New Testament, which were primarily letters from the Apostles to the Christian communities of the ancient world, and which were, from the start, intended for a liturgical setting. 

The second reading is followed by the Alleluia, the Hebrew word meaning “praise the Lord” used repeatedly in the Book of Revelation. Whether said or sung, the word calls the congregation to abandon our posture of sitting (a gesture of receptivity) and stand out of respect for Christ, who will become even more immediately present in the Gospel reading. 

Then, a priest or deacon proclaims the Gospel, meaning “Good News.” Taken from one of the four Gospels in the New Testament, the Gospel often echoes themes from the earlier readings, demonstrating the Church’s ancient understanding that the New and Old Testaments are only fully understood in light of each other.

The homily 

In the homily, the priest follows the example of Christ on the road to Emmaus, explaining and interpreting the Scriptures. Sometimes this interpretation is biblical, sometimes theological, sometimes moral or catechetical (Lk 24:13-35). Always, however, again in imitation of the Emmaus encounter (where Christ “was made known … in the Breaking of the Bread”), it should prepare the congregation for or point us toward what is about to follow: the Liturgy of the Eucharist. 

The Credo and prayers of the faithful 

Before the second part of the Mass begins, however, the congregation first rises to make our profession of faith. The Credo, literally “I believe,” is a summation of Catholic belief. Each word is weighted with meaning and was the subject of much theological wrestling in the first three centuries after Christ. 

The Creed most commonly recited today is the Nicene Creed (or more accurately the Nicene-Constantinopolitan Creed), having emerged from the Councils of Nicaea (325) and Constantinople (381). When Catholics proclaim the Creed, we do so as a testimony to our personal faith, as well as to the unity of the Faith across space and time. It is a sign of communion with Catholics in the next pew, in fourth-century Antioch and in the heavenly courts. 

Notably, in the middle of the Credo, at the words, “and by the power of the Holy Spirit was incarnate of the Virgin Mary,” the congregations solemnly bows, acknowledging the pre-eminent importance of the Incarnation. 

The Credo is followed by the prayers of the faithful or the general intercessions of the Mass. 

In obedience to St. Paul’s request in 1 Timothy 2:1-3, the Church offers “supplications, prayers, petitions, and thanksgiving for everyone,” beginning with petitions for the needs of the Church, then public authorities and those oppressed by any need, and finally the local community. 

Part II: The Liturgy of the Eucharist  

The offertory 

Every sacrifice requires an offering, and the Holy Sacrifice of the Mass is no exception. 

On Sundays, at the beginning of the Liturgy of the Eucharist, there is a collection, with the congregation placing our individual offerings in a basket. Today, those offerings take the form of cash or check. In third-century Rome, St. Hippolytus tells us, they included grapes, figs, apples, even lilies — anything that could support the community. Tertullian, writing from second-century Carthage, likewise said that the donations went toward burying the poor, supplying the wants of orphans, and providing for the homebound. 

The collection is then carried up into the sanctuary, often with the bread and wine to be consecrated. Together, they represent the fruits of the earth offered by man, its steward. They also represent the spiritual offering of the faithful, the offering of our lives to Christ. 

Preparation of the gifts 

While the collection is taken up, the priest prepares the altar. When all is ready, he elevates first the bread, then the wine, pronouncing a blessing over each. The blessing, which begins, “Blessed are you, Lord of all creation,” echoes the blessing Jesus pronounced at the Last Supper, the blessing of the Passover meal, “Blessed are you, Lord our God, king of the universe, creator of the fruit of the vine.” It also echoes the blessing of Melchizedek in Genesis 14: 19-20. 

Importantly, before pronouncing the blessing over the wine, the priest mixes into it a small amount of water. He does this in continuation of the custom of Jesus’ time, where wine was diluted before it was drunk, and as a symbol of the blood and water that gushed forth from Christ’s side on the cross (Jn 19:34). 

Next, the priest washes his hands, following St. Paul’s advice in 1 Timothy 2:8, that when praying, men should lift up “holy” or “clean” hands. 

Finally, with the priest, the whole congregation implores God to accept the sacrifices offered — both the priest’s and our own — and, by it, bless the world. 

Preface and the Sanctus 

The preface of the Eucharistic Liturgy has remained virtually unchanged for the past 1800 years. In the early 200s, St. Hippolytus’ account of the Mass in Rome included the dialogue between priest and people that enjoins the congregation to “Lift up your hearts to the Lord” and “Give thanks to the Lord our God.” His contemporary in North Africa, St. Cyprian, records the same dialogue in his description of the liturgy, a dialogue intended to remind Christians that “wherever your treasure is, there will your heart be also” (Mt 6:21). 

The preface continues with a short prayer. Like the opening dialogue, it focuses the congregation on the importance of what is about to take place and invites us to enter into the Mass even more completely. 

Then, with the reminder that we are praying “with the angels and saints,” the congregation sings the Sanctus, the “Holy, Holy, Holy,” taken from Isaiah 6:2-3 and Revelation 4:8. This hymn, as we know from a letter from Pope St. Clement (martyred in A.D. 99), has been sung in the Mass since at least the first century of Christianity. 

The Eucharistic Prayer 

After the Sanctus, the congregation kneels, assuming a posture of reverence in preparation for the central act of the Mass. The priest then prays the Eucharistic Prayer, or Canon. 

For this prayer, the priest has four options: Eucharistic Prayer 1, published in 1570 but virtually identical to the Eucharistic prayer used by St. Ambrose in the fourth century and St. Augustine in the fifth century; Eucharistic Prayer 2, drawn from the Greek liturgy of St. Hippolytus in 215; Eucharistic Prayer 3, an abbreviated twentieth-century version of Eucharistic Prayer 1; and Eucharistic Prayer 4, a 20th-century prayer adapted from the ancient liturgies of the Eastern Churches. 

Although the prayers differ in length and phrasing, they all have the following in common. 

Each offers thanksgiving and praise to God. 

Each includes a prayer for the sending down of the Holy Spirit, the epiclesis, for nothing in the Eucharistic sacrifice happens by man’s effort alone. 

Each includes an institution narrative (the story of the Last Supper) followed by the words of consecration, taken from the Gospels of Matthew, Mark, and Luke, as well as 1 Corinthians 11:23-26.

 Each also includes the elevation, first the sacred Host, then the sacred Chalice, often to the sounds of ringing bells, proclaiming that a great miracle has occurred: Bread and wine are no longer bread and wine. Christ is now present in the Eucharist, Body, Blood, Soul and Divinity. 

And each includes the mystery of faith, a summary of the paschal mystery, which affirms the reality of Christ’s passion, death, and resurrection, the saving power of the mystery unfolding before us, and the anticipated second coming of Christ. 

Finally, each concludes with a closing doxology, the Great Amen. “Amen” is a Hebrew word that in this context means “truly” or “yes,” and conveys the congregation’s agreement with the entirety of the Eucharistic Prayer, as well as a “yes” to Christ, elevated on the altar. 

The Lord’s Prayer 

In preparation for holy Communion, the congregation stands and, with the priest, prays the Our Father. This prayer, taught by Jesus to his disciples in Luke 11:1-4, has been a part of the Mass since at least the second century. It’s there both as a reminder that our relationship with God is essentially familial — he is our Father — and as an act of supplication for “our daily bread” — the Holy Eucharist. 

The sign of peace 

Christ adjured his followers that before they could approach the altar, they first needed to be reconciled with their brother (Mt 5:23-24). Likewise both Paul and Peter instructed the early Christians to “Greet one another with a holy kiss” (Rom 16:16; 1 Pet 5:14). 

From the first century, when Justin Martyr wrote about it in his account of the Mass, both injunctions were heeded through the sign of peace, a ritual gesture (typically a handshake, embrace, or solemn bow) that says we are at peace with our neighbor. 

The Agnus Dei and Domine, Non Sum Dignus 

In Revelation, the saints and angels worship the Lamb, and in John 1:29 we hear John the Baptist cry, “Behold the Lamb of God.”  

That is exactly what the congregation does as the Agnus Dei or “Lamb of God” prayer is uttered. Three times, using a formula of prayer introduced into the Mass by the seventh-century Syrian pope, St. Sergius, we implore Christ, the Lamb of God, for mercy. 

Traditionally in the West, we then drop to our knees and adore him, as the priest repeats the words of John 1 and Revelation 19:9: “Behold the Lamb of God. Behold him who takes away the sin of the world. Blessed are those called to the Supper of the Lamb.” 

The congregation answers in turn with the Domine, non sum dignus, the words of the centurion in Matthew 8:8: “Lord, I am not worthy that you should enter under my roof, but only say the word and my soul shall be healed.” That answer, like the centurion’s, is an act of faith, a profession of belief that there are no wounds of mind, body, or soul which Christ cannot heal. 

Holy Communion 

Healing comes in holy Communion, when the faithful receive the Body and Blood of Christ. 

The rite today is an exact image of the early Church’s. As St. Ambrose in the fourth century wrote, “The priest says to you ‘The Body of Christ’ and you say, ‘Amen.’” 

Communion may be received by all Catholics in good standing with the Church, who are not in a state of mortal sin and who have fasted for at least one hour. 

It may be received on the tongue or in the hand, standing or kneeling, and with a solemn bow or genuflection preceding reception. 

Communion is frequently offered under both species, Body and Blood, but the faithful need only receive under one kind to receive the fullness of both. 

After all have received Communion, the priest cleanses the Communion vessels, and offers a brief prayer.

The dismissal 

Then, almost too quickly, it’s over. The priest dismisses the congregation, blessing them once more with the Sign of the Cross and charging them to live what they have received.  

To do that, he says the same words which have dismissed the faithful since the days of the catacombs: Ite, missa est, translated as “The Mass is ended. Go in peace to love and serve the Lord.”

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