Today’s Catechism sections discuss the signs of bread and wine and the institution of the Eucharist. Supporting material comes from the “Summa Theologica”.

III. The Eucharist in the Economy of Salvation

The signs of bread and wine

1333 At the heart of the Eucharistic celebration are the bread and wine that, by the words of Christ and the invocation of the Holy Spirit, become Christ's Body and Blood. Faithful to the Lord's command the Church continues to do, in his memory and until his glorious return, what he did on the eve of his Passion: "He took bread...." "He took the cup filled with wine...." the signs of bread and wine become, in a way surpassing understanding, the Body and Blood of Christ; they continue also to signify the goodness of creation. Thus in the Offertory we give thanks to the Creator for bread and wine,152 fruit of the "work of human hands," but above all as "fruit of the earth" and "of the vine" - gifts of the Creator. The Church sees in the gesture of the king-priest Melchizedek, who "brought out bread and wine," a prefiguring of her own offering.153

1334 In the Old Covenant bread and wine were offered in sacrifice among the first fruits of the earth as a sign of grateful acknowledgment to the Creator. But they also received a new significance in the context of the Exodus: the unleavened bread that Israel eats every year at Passover commemorates the haste of the departure that liberated them from Egypt; the remembrance of the manna in the desert will always recall to Israel that it lives by the bread of the Word of God;154 their daily bread is the fruit of the promised land, the pledge of God's faithfulness to his promises.
The "cup of blessing"155 at the end of the Jewish Passover meal adds to the festive joy of wine an eschatological dimension: the messianic expectation of the rebuilding of Jerusalem. When Jesus instituted the Eucharist, he gave a new and definitive meaning to the blessing of the bread and the cup.

1335 The miracles of the multiplication of the loaves, when the Lord says the blessing, breaks and distributes the loaves through his disciples to feed the multitude, prefigure the superabundance of this unique bread of his Eucharist.156 The sign of water turned into wine at Cana already announces the Hour of Jesus' glorification. It makes manifest the fulfillment of the wedding feast in the Father's kingdom, where the faithful will drink the new wine that has become the Blood of Christ.157

1336 The first announcement of the Eucharist divided the disciples, just as the announcement of the Passion scandalized them: "This is a hard saying; who can listen to it?"158 The Eucharist and the Cross are stumbling blocks. It is the same mystery and it never ceases to be an occasion of division. "Will you also go away?":159 The Lord's question echoes through the ages, as a loving invitation to discover that only he has "the words of eternal life"160 and that to receive in faith the gift of his Eucharist is to receive the Lord himself.

The institution of the Eucharist

1337 The Lord, having loved those who were his own, loved them to the end. Knowing that the hour had come to leave this world and return to the Father, in the course of a meal he washed their feet and gave them the commandment of love.161 In order to leave them a pledge of this love, in order never to depart from his own and to make them sharers in his Passover, he instituted the Eucharist as the memorial of his death and Resurrection, and commanded his apostles to celebrate it until his return; "thereby he constituted them priests of the New Testament."162

1338 The three synoptic Gospels and St. Paul have handed on to us the account of the institution of the Eucharist; St. John, for his part, reports the words of Jesus in the synagogue of Capernaum that prepare for the institution of the Eucharist: Christ calls himself the bread of life, come down from heaven.163

1339 Jesus chose the time of Passover to fulfill what he had announced at Capernaum: giving his disciples his Body and his Blood:

Then came the day of Unleavened Bread, on which the passover lamb had to be sacrificed. So Jesus sent Peter and John, saying, "Go and prepare the passover meal for us, that we may eat it...." They went ... and prepared the passover. And when the hour came, he sat at table, and the apostles with him. And he said to them, "I have earnestly desired to eat this passover with you before I suffer; for I tell you I shall not eat it again until it is fulfilled in the kingdom of God.".... And he took bread, and when he had given thanks he broke it and gave it to them, saying, "This is my body which is given for you. Do this in remembrance of me." and likewise the cup after supper, saying, "This cup which is poured out for you is the New Covenant in my blood."164

1340 By celebrating the Last Supper with his apostles in the course of the Passover meal, Jesus gave the Jewish Passover its definitive meaning. Jesus' passing over to his father by his death and Resurrection, the new Passover, is anticipated in the Supper and celebrated in the Eucharist, which fulfills the Jewish Passover and anticipates the final Passover of the Church in the glory of the kingdom.

In the “Summa Theologica” (3, 73, 5), St. Thomas Aquinas discusses the institution of the Eucharist.

Article 5. Whether the institution of this sacrament was appropriate?

Objection 1. It seems that the institution of this sacrament was not appropriate, because as thePhilosopher says (De Gener. ii): "We are nourished by the things from whence we spring." But byBaptism, which is spiritual regeneration, we receive our spiritual being, as Dionysius says (Eccl. Hier. ii). Therefore we are also nourished by Baptism. Consequently there was no need to institute thissacrament as spiritual nourishment.

Objection 2. Further, men are united with Christ through this sacrament as the members with the head. But Christ is the Head of all men, even of those who have existed from the beginning of the world, as stated above (8, 3,6). Therefore the institution of this sacrament should not have been postponed till the Lord's supper.

Objection 3. Further, this sacrament is called the memorial of our Lord's Passion, according to Matthew 26 (Luke 22:19): "Do this for a commemoration of Me." But a commemoration is of things past. Therefore, this sacrament should not have been instituted before Christ's Passion.

Objection 4. Further, a man is prepared by Baptism for the Eucharist, which ought to be given only to the baptized. But Baptism was instituted by Christ after His Passion and Resurrection, as is evident from Matthew 28:19. Therefore, this sacrament was not suitably instituted before Christ's Passion.

On the contrary, This sacrament was instituted by Christ, of Whom it is said (Mark 7:37) that "He did all things well."

I answer that, This sacrament was appropriately instituted at the supper, when Christ conversed with His disciples for the last time. First of all, because of what is contained in the sacrament: for Christ is Himself contained in the Eucharist sacramentally. Consequently, when Christ was going to leave Hisdisciples in His proper species, He left Himself with them under the sacramental species; as theEmperor's image is set up to be reverenced in his absence. Hence Eusebius says: "Since He was going to withdraw His assumed body from their eyes, and bear it away to the stars, it was needful that on the day of the supper He should consecrate the sacrament of His body and blood for our sakes, in order that what was once offered up for our ransom should be fittingly worshiped in a mystery."

Secondly, because without faith in the Passion there could never be any salvation, according to Romans 3:25: "Whom God hath proposed to be a propitiation, through faith in His blood." It was necessaryaccordingly that there should be at all times among men something to show forth our Lord's Passion; the chief sacrament of which in the old Law was the Paschal Lamb. Hence the Apostle says (1 Corinthians 5:7): "Christ our Pasch is sacrificed." But its successor under the New Testament is thesacrament of the Eucharist, which is a remembrance of the Passion now past, just as the other was figurative of the Passion to come. And so it was fitting that when the hour of the Passion was come,Christ should institute a new Sacrament after celebrating the old, as Pope Leo I says (Serm. lviii).

Thirdly, because last words, chiefly such as are spoken by departing friends, are committed most deeply to memory; since then especially affection for friends is more enkindled, and the things which affect us most are impressed the deepest in the soul. Consequently, since, as Pope Alexander I says, "amongsacrifices there can be none greater than the body and blood of Christ, nor any more powerful oblation";our Lord instituted this sacrament at His last parting with His disciples, in order that it might be held in the greater veneration. And this is what Augustine says (Respons. ad Januar. i): "In order to commend more earnestly the death of this mystery, our Saviour willed this last act to be fixed in the hearts and memories of the disciples whom He was about to quit for the Passion."

Reply to Objection 1. We are nourished from the same things of which we are made, but they do not come to us in the same way; for those out of which we are made come to us through generation, while the same, as nourishing us, come to us through being eaten. Hence, as we are new-born in Christthrough Baptism, so through the Eucharist we eat Christ.

Reply to Objection 2. The Eucharist is the perfect sacrament of our Lord's Passion, as containing Christcrucified; consequently it could not be instituted before Incarnation; but then there was room for only such sacraments as were prefigurative of the Lord's Passion.

Reply to Objection 3. This sacrament was instituted during the supper, so as in the future to be a memorial of our Lord's Passion as accomplished. Hence He said expressively: "As often as ye shall do these things" [Cf. Canon of the Mass, speaking of the future.

Reply to Objection 4. The institution responds to the order of intention. But the sacrament of theEucharist, although after Baptism in the receiving, is yet previous to it in intention; and therefore it behooved to be instituted first. or else it can be said that Baptism was already instituted in Christ'sBaptism; hence some were already baptized with Christ's Baptism, as we read in John 3:22.

Footnotes

152 Cf. ⇒ Ps 104:13-15.
153 ⇒ Gen 14:18; cf. Roman Missal, EP I (Roman Canon) 95.
154 Cf. ⇒ Deut 8:3.
155 ⇒ 1 Cor 10:16.
156 Cf. ⇒ Mt 14:13-21; ⇒ 15:32-39.
157 Cf. ⇒ Jn 2:11; ⇒ Mk 14:25.
158 ⇒ Jn 6:60.
159 ⇒ Jn 6:67.
160 In 6:68.
161 Cf. ⇒ Jn 13:1-17; ⇒ 34-35.
162 Council of Trent (1562): DS 1740.
163 Cf. ⇒ Jn 6.
164 ⇒ Lk 22:7-20; Cf. ⇒ Mt 26:17-29; ⇒ Mk 14:12-25; ⇒ 1 Cor 11:23-26.