An Introduction to the Mass and the Eucharist
Welcome to this short introduction to the celebration of the Holy Mass, or Eucharist (which means thanksgiving)! The Eucharist is the source and summit of the Christian life and its highest and most important prayer. In the Mass the whole mystery of our salvation is made present; in the Eucharist we receive the Body and Blood of Jesus our Lord, who is really and truly present under the appearance of bread and wine and who gives himself to us in this great gift of love.
This short guide will help you to understand the Mass so that you can better prepare yourself to take a part in its celebration. We will answer the following questions: What is the origin of the Mass? What exactly is the Eucharist? What are the fruits of Holy Communion in the lives of those who receive it? What are the main parts of the Mass? Who can and who cannot receive Holy Communion?
What is the Origin of the Mass?
The signs of bread and wine, which signify the goodness of creation, go all the way back to Melchizedek, priest of God most high, who brought an offering of bread and wine to Abraham (Gen 14:18). In the Old Testament bread and wine were offered in sacrifice among the first fruits of the earth as a sign of grateful acknowledgement to the Creator. 
At the time of the Exodus, the deliverance out of Egypt began when the Israelites slaughtered a young lamb, put its blood on the doorpost of their houses, and then had to eat the Lamb for them to be protected from the angel of death (Ex 12). The Exodus also gave a special significance to the signs of bread and wine: the unleavened bread that Israel eats every year at Passover commemorates the haste of their departure from Egypt; the remembrance of the manna in the desert recalls to Israel that it lives by the bread of the Word of God. And the “cup of blessing” at the end of the Passover meal adds to the festive joy of wine the messianic expectation of the rebuilding of Jerusalem. 
When Jesus began his public ministry, John the Baptist called him the “Lamb of God” (John 1:36) – a name that pointed to his future self-offering as a sacrifice for our sins. Jesus also called himself the “living bread that came down from heaven” and promised that they who would eat this bread would live forever (John 6:51). He said: “Unless you eat the flesh of the Son of Man and drink his blood, you have no life in you. Whoever eats my flesh and drinks my blood has eternal life, and I will raise him up at the last day. For my flesh is food indeed, and my blood is drink indeed” (John 6:53-55). This was such a shocking teaching that many of his disciples were scandalized and left him after hearing it (Jn 6:66) – and so the Eucharist and the cross remain stumbling blocks and an occasion of division even today. Yet the Lord asks us: “Will you also go away?” (John 6:67) as a loving invitation to discover that only he has the words of eternal life and that to receive in faith the gift of the Eucharist is to receive the Lord himself and the eternal life he has come to share with us.
On the eve of his passion and death, Jesus ate his last Passover meal with his apostles, and he transformed this Last Supper into the memorial of his voluntary offering to the Father for the salvation of the world. By instituting the Eucharist he also instituted a New Covenant with the house of Israel, giving a new and definitive meaning to the blessing of the bread and the cup by saying: “This is my body… this is my blood of the new covenant, which is shed for many for the remission of sins” (Mt 26:26-27). The following day, Jesus’ death on the cross became the definitive Paschal sacrifice for the redemption of mankind and the sacrifice of the New Covenant which reconciles man to God and restores man to communion with Him.
At the Last Supper, Jesus told his apostles to “do this in remembrance of me” (Luke 22:19) – that is to repeat his actions and words until he returns. This does not only mean to remember what Jesus did; it also points to the liturgical celebration, by the apostles and their successors, of Christ’s life, death and resurrection.
What is the Eucharist?
When we celebrate the memorial of the Lord’s sacrifice, we offer to the Father what he has himself given us: the gifts of his creation, bread and wine which have become the body and blood of Christ. The Eucharist is therefore:
- Thanksgiving and praise to God the Father;
- The sacrificial memorial of Christ and his body;
- The presence of Christ by the power of his word and of his Spirit.
- Thanksgiving and praise to the Father: The Eucharist is a sacrifice of thanksgiving to the Father for all that he accomplished in his work of creation, in redeeming us, and in making us holy. It is also a sacrifice of praise by which the Church sings the glory of God in the name of all creation. 
- The Sacrificial Memorial of Christ and his Body, the Church: The Eucharist makes present in a real way Christ’s unique sacrifice at the cross, in a way similar to how the events of the Exodus are made present every time Passover is celebrated. Although Christ’s unique sacrifice happened only once, his sacrifice transcends time, and so every time we celebrate the Eucharist it is made present to us. At Mass, we are literally at the foot of the cross: the sacrifice of Christ and the sacrifice of the Eucharist are one single sacrifice in which we, the Body of Christ, also take an active part by being joined to Christ’s sacrifice. By uniting our lives, our praise, sufferings, prayer, and work to those of Christ, we can “fill up in our flesh what is lacking in the afflictions of Christ, for the sake of his body, which is the Church” (Col 1:24). When we celebrate Mass we are also united with the whole Church on earth (the pope, bishops, clergy and all the faithful), in heaven (the Blessed Virgin Mary, the angels and all the saints), and we also pray for those who have died in Christ but are not yet wholly purified, so that they may be able to enter into the light and peace of Christ. 
- The Presence of Christ by the power of his word and the Holy Spirit: Jesus is present in many ways to the Church, but he is present most especially in the Eucharist. In the Eucharist the body and blood, the soul and divinity of Christ, and therefore the whole Christ is truly, really and entirely present. How does this happen? It is a mystery that we cannot fully understand. But in faithfulness to Jesus’ words (Jn 6:55, Mt 26:26-27), the Church has always believed that at the time of the consecration of the bread and wine by the priest, there is a change of the whole substance of the bread and wine into the substance of the body and blood of Christ In other words, the Eucharist continues to appear under the form, color and taste of bread and wine, but in reality they are no longer bread and wine but truly the body and blood of Christ. 
The Eucharist is God’s greatest gift to us. Throughout the history of salvation, God has always wished to be present with us, to dwell with us and even in us – to be “Immanuel” – God is with us. In the Old Testament, his Real Presence dwelt in the Ark of the Covenant in the Holy of Holies, but nobody could approach it because of the gap between God’s holiness and the people’s sinfulness. When Jesus came to reconcile us with the Father, he opened the way for us into the Holy of Holies: now not only we can approach God freely as our Father, we can also receive into us Him who has loved us to the end. And so the Eucharist is also a joyful banquet of communion and intimate union of the faithful with Christ himself who has offered himself to us.
The Eucharist is usually kept in the tabernacle of most Catholic churches – a small box at the front of the church usually with a lit candle besides it to indicate the Lord’s presence. The name 'tabernacle' reminds us of the tabernacle in the desert, God's dwelling among His people Israel as they wandered through the desert towards the Promised Land. In those times God dwellt in the Holy of Holies and was inapproachable except for once a year by the high priest. Now His Real Presence is accessible to all in the tabernacle of every Catholic Church. When we stand before His Presence in the tabernacle, it is as if we stand before the Holy of Holies of the ancient tabernacle. Because God is truly present in the Eucharist, we usually make a sign of reverence before the tabernacle, either by genuflecting or bowing. Jesus also invites us and awaits us in this sacrament of love to come pray and adore him. Quiet time before the Lord’s presence in the Eucharist is one of the best ways to deepen our relationship with him and to find quiet and peace from the troubles and worries of everyday life.
The Fruits of Holy Communion
What does the Eucharist do to those who receive it frequently?
- Holy Communion augments our union with Christ. The principal fruit of receiving the Eucharist is an intimate union with the Lord. Jesus said: “He who eats My flesh and drinks My blood abides in Me, and I in him” (Jn 6:56). The Eucharist preserves, increases, and renews the life of grace that we received at baptism.
- Holy Communion separates us from sin: by uniting us with Christ and by being spiritual food which strengthens our charity, the Eucharist wipes away venial sins and preserves us from future mortal sins. The more we share the life of Christ, the more difficult it is to break away from him through serious sin.
- Holy Communion strengthens the unity of the Church, the Mystical Body of Christ. When we receive the Eucharist, Christ renews, strengthens and deepens our incorporation into the Church: “The bread which we break, is it not the communion of the body of Christ? For we, though many, are one bread and one body; for we all partake of that one bread” (1 Cor 10:16-17).
- Holy Communion commits us to serving the poor. 
What are the main parts of the Mass?
Since the earliest days of the Church, the Mass has kept the same basic structure. It is composed of two principal parts:
In the Liturgy of the Word, we listen to the Word of God from the Bible and respond to it with acclamations and a psalm. Hearing God’s Word increases our faith and understanding of the mystery of salvation before we take a direct part in it through the Eucharist.
In the Liturgy of the Eucharist, the elements of bread and wine are brought to the altar, and through the Eucharistic prayer of the priest(s) they become the body and blood of the Lord Jesus who wishes to give himself to us. 
The Liturgy of the Word
[Parts in brackets are said on Sundays and feast days only]
- The Sign of the Cross: we gather with the sign of our faith, in the name of the Father, of the Son, and of the Holy Spirit, the One God who is three Persons.
- The penitential rite (“Lord, have mercy!”) and priest’s absolution: we implore the Lord’s mercy and confess that we have sinned before coming before him.
- [The Gloria: we glorify God with this hymn of praise ]
- The first reading is usually from the Old Testament, but sometimes from a book of the New Testament
- The responsorial psalm is read or sung by the congregation to foster meditation on the Word of God
- [The second reading is usually from a book of the New Testament]
- In the Alleluia, we welcome the Lord who is about to speak to us in the Gospel.
- The Gospel, read by the priest or deacon, is the high point of the liturgy of the word.
- The homily is a teaching on the readings given by the priest.
- [We then recite the creed, the profession of the essential pillars of our faith.]
- In the general intercessions, we offer our prayers for the needs of the Church and the salvation of the world.
The Liturgy of the Eucharist
- The presentation of the offerings: the gifts of bread and wine are brought to the altar, and a collection is taken, where we bring our gifts for the poor and for the Church.
- The preparation of the gifts: the Jewish blessings are said over the bread and wine.
- The Eucharistic Prayer is a long prayer of thanksgiving and consecration which is the heart and summit of the celebration. It includes:
- The Sanctus (Kadosh): we praise the holiness of the Lord with all the angels and saints
- The Epiclesis: the priest asks the Father to send his Spirit on the bread and wine so that they may become the body and blood of Jesus.
- The Institution Narrative: the words of Christ and the power of the Holy Spirit make present the Lord’s body and blood
- The Memorial Acclamation: we proclaim Jesus’ death, resurrection and expected second coming.
- The Anamnesis: the Church presents to the Father the offering of his Son.
- The Intercessions: the Eucharist is celebrated with the whole Church in heaven and on earth.
- The Doxology and Great Amen: we give glory and honor to God for his gifts.
- The Lord’s Prayer: we ask God our Father to care of all our needs.
- The Sign of Peace: The Church asks for peace and unity for herself and for the whole human family.
- The Lamb of God is sung as the priest breaks the bread, signifying the Lord’s broken body for us.
- At Communion, we receive the Lord’s body and blood which is a source of life, love and holiness.
- The concluding rite: the priest dismisses the faithful to go out and spread the good news that we have just received.
Who can celebrate the Eucharist?
Only validly ordained priests can preside at the Eucharist and consecrate the bread and the wine so that they become the Body and Blood of the Lord.  When Jesus instituted the Eucharist, not all of his disciples were present but only his twelve apostles. Although all believers in Jesus form a “kingdom of priests,” Jesus only gave to the apostles and to their successors (bishops and priests) the authority to celebrate the Eucharist in his name – just as in the Old Testament only the Aaronic priests could offer sacrifices even though all of Israel was a “kingdom of priests and a holy nation” (Ex 19:6).
Who can receive Holy Communion?
We welcome Catholics to participate fully in the celebration of the Eucharist by receiving Holy Communion in fulfillment of Christ's command to eat His body and drink His blood (Jn 6:51). In order to be properly disposed to receive Communion, communicants should not be conscious of grave sin, have fasted for an hour before Communion, and seek to live in charity and love with their neighbors. Those conscious of grave sin must first be reconciled with God and the Church through the sacrament of Penance. A frequent reception of the sacrament of Penance is encouraged for all. 
Attending Mass on Saturday evening or Sunday (and on important feast days) is obligatory for Catholics, in fulfillment of the third (or fourth) commandment to sanctify the Sabbath (or Lord’s Day). A Catholic who deliberately misses Mass on these days commits a grave sin and should receive the sacrament of Penance before he returns to the table of the Eucharist. 
For Baptized Believers in Jesus who are not Catholics
We welcome you to attend the celebration of the Eucharist as our brothers and sisters in Messiah, even though we do not yet have full unity and communion between us. We pray that our common baptism and the action of the Holy Spirit in this Eucharist will draw us closer to one another and begin to dispel the sad divisions which separate us. We pray that these will lessen and finally disappear, in keeping with Christ’s prayer for us “that they may all be one” (Jn 17:21).
Because the Eucharist is a sign of the oneness and unity of our faith, life and worship, we unfortunately cannot extend to you an invitation to receive Communion.  Since non-Catholic believers do not usually share our faith regarding the nature of the Church, the priesthood, and the Real Presence of Christ in the Eucharist, sharing Communion together would imply a oneness which does not yet exist, and for which we must all pray. If you would like to learn more about the Catholic faith and how you could receive the Eucharist, please ask a priest or a helper and they will gladly answer your questions.
We also welcome to this celebration those who do not share our faith in Jesus Christ. While we cannot admit them to Holy Communion, we ask them to offer their prayers for the peace, unity, conversion and salvation of the human family.
For those not receiving Holy Communion
All who are not receiving Holy Communion are encouraged to express in their hearts a prayerful desire for unity with the Lord Jesus and with one another.