Summa Th. III EN Qu.72 a.10

Whether he who is confirmed needs one to stand* for him? [*Literally, "to hold him"]

Objection: 1. It seems that he who is confirmed needs no one to stand for him. For this sacrament is given not only to children but also to adults. But adults can stand for themselves. Therefore it is absurd that someone else should stand for them.
2. Further, he that belongs already to the Church, has free access to the prince of the Church, i.e. the bishop. But this sacrament, as stated above (Article [6]), is given only to one that is baptized, who is already a member of the Church. Therefore it seems that he should not be brought by another to the bishop in order to receive this sacrament.
3. Further, this sacrament is given for spiritual strength, which has more vigor in men than in women, according to Pr 31,10: "Who shall find a valiant woman?" Therefore at least a woman should not stand for a man in confirmation.

On the contrary Are the following words of Pope Innocent, which are to be found in the Decretals (XXX, Question [4]): "If anyone raise the children of another's marriage from the sacred font, or stand for them in Confirmation," etc. Therefore, just as someone is required as sponsor of one who is baptized, so is someone required to stand for him who is to be confirmed .
I answer that As stated above (Articles [1],4,9), this sacrament is given to man for strength in the spiritual combat. Now, just as one newly born requires someone to teach him things pertaining to ordinary conduct, according to He 12,9: "We have had fathers of our flesh, for instructors, and we obeyed [Vulg.: 'reverenced']" them; so they who are chosen for the fight need instructors by whom they are informed of things concerning the conduct of the battle, and hence in earthly wars, generals and captains are appointed to the command of the others. For this reason he also who receives this sacrament, has someone to stand for him, who, as it were, has to instruct him concerning the fight.Likewise, since this sacrament bestows on man the perfection of spiritual age, as stated above (Articles [2],5), therefore he who approaches this sacrament is upheld by another, as being spiritually a weakling and a child.

Reply to Objection: 1. Although he who is confirmed, be adult in body, nevertheless he is not yet spiritually adult.
2. Though he who is baptized is made a member of the Church, nevertheless he is not yet enrolled as a Christian soldier. And therefore he is brought to the bishop, as to the commander of the army, by one who is already enrolled as a Christian soldier. For one who is not yet confirmed should not stand for another in Confirmation.
3. According to Col 3 *(Ga 3,28), "in Christ Jesus there is neither male nor female." Consequently it matters not whether a man or a woman stand for one who is to be confirmed.

Whether only a bishop can confer this sacrament?

Objection: 1. It seems that not only a bishop can confer this sacrament. For Gregory (Regist. iv), writing to Bishop Januarius, says: "We hear that some were scandalized because we forbade priests to anoint with chrism those who have been baptized. Yet in doing this we followed the ancient custom of our Church: but if this trouble some so very much we permit priests, where no bishop is to be had, to anoint the baptized on the forehead with chrism." But that which is essential to the sacraments should not be changed for the purpose of avoiding scandal. Therefore it seems that it is not essential to this sacrament that it be conferred by a bishop.
2. Further, the sacrament of Baptism seems to be more efficacious than the sacrament of Confirmation: since it bestows full remission of sins, both as to guilt and as to punishment, whereas this sacrament does not. But a simple priest, in virtue of his office, can give the sacrament of Baptism: and in a case of necessity anyone, even without orders, can baptize. Therefore it is not essential to this sacrament that it be conferred by a bishop.
3. Further, the top of the head, where according to medical men the reason is situated (i.e. the "particular reason," which is called the "cogitative faculty"), is more noble than the forehead, which is the site of the imagination. But a simple priest can anoint the baptized with chrism on the top of the head. Therefore much more can he anoint them with chrism on the forehead, which belongs to this sacrament.

On the contrary Pope Eusebius (Ep. iii ad Ep. Tusc.) says: "The sacrament of the imposition of the hand should be held in great veneration, and can be given by none but the high priests. Nor is it related or known to have been conf erred in apostolic times by others than the apostles themselves; nor can it ever be either licitly or validly performed by others than those who stand in their place. And if anyone presume to do otherwise, it must be considered null and void; nor will such a thing ever be counted among the sacraments of the Church." Therefore it is essential to this sacrament, which is called "the sacrament of the imposition of the hand," that it be given by a bishop.
I answer that In every work the final completion is reserved to the supreme act or power; thus the preparation of the matter belongs to the lower craftsmen, the higher gives the form, but the highest of all is he to whom pertains the use, which is the end of things made by art; thus also the letter which is written by the clerk, is signed by his employer. Now the faithful of Christ are a Divine work, according to 1Co 3,9: "You are God's building"; and they are also "an epistle," as it were, "written with the Spirit of God," according to 2Co 3,2-3. And this sacrament of Confirmation is, as it were, the final completion of the sacrament of Baptism; in the sense that by Baptism man is built up into a spiritual dwelling, and is written like a spiritual letter; whereas by the sacrament of Confirmation, like a house already built, he is consecrated as a temple of the Holy Ghost, and as a letter already written, is signed with the sign of the cross. Therefore the conferring of this sacrament is reserved to bishops, who possess supreme power in the Church: just as in the primitive Church, the fulness of the Holy Ghost was given by the apostles, in whose place the bishops stand (Ac 8). Hence Pope Urban I says: "All the faithful should. after Baptism, receive the Holy Ghost by the imposition of the bishop's hand, that they may become perfect Christians."

Reply to Objection: 1. The Pope has the plenitude of power in the Church, in virtue of which he can commit to certain lower orders things that belong to the higher orders: thus he allows priests to confer minor orders, which belong to the episcopal power. And in virtue of this fulness of power the Pope, Blessed Gregory, allowed simple priests to confer this sacrament, so long as the scandal was ended.
2. The sacrament of Baptism is more efficacious than this sacrament as to the removal of evil, since it is a spiritual birth, that consists in change from non-being to being. But this sacrament is more efficacious for progress in good; since it is a spiritual growth from imperfect being to perfect being. And hence this sacrament is committed to a more worthy minister.
3. As Rabanus says (De Instit. Cleric. i), "the baptized is signed by the priest with chrism on the top of the head, but by the bishop on the forehead; that the former unction may symbolize the descent of the Holy Ghost on hint, in order to consecrate a dwelling to God: and that the second also may teach us that the sevenfold grace of the same Holy Ghost descends on man with all fulness of sanctity, knowledge and virtue." Hence this unction is reserved to bishops, not on account of its being applied to a more worthy part of the body, but by reason of its having a more powerful effect.

Whether the rite of this sacrament is appropriate?

Objection: 1. It seems that the rite of this sacrament is not appropriate. For the sacrament of Baptism is of greater necessity than this, as stated above (Article [2], ad 4; Question [65], Articles [3],4). But certain seasons are fixed for Baptism, viz. Easter and Pentecost. Therefore some fixed time of the year should be chosen for this sacrament.
2. Further, just as this sacrament requires devotion both in the giver and in the receiver, so also does the sacrament of Baptism. But in the sacrament of Baptism it is not necessary that it should be received or given fasting. Therefore it seems unfitting for the Council of Orleans to declare that "those who come to Confirmation should be fasting"; and the Council of Meaux, "that bishops should not give the Holy Ghost with imposition of the hand except they be fasting."
3. Further, chrism is a sign of the fulness of the Holy Ghost, as stated above (Article [2]). But the fulness of the Holy Ghost was given to Christ's faithful on the day of Pentecost, as related in Ac 2,1. Therefore the chrism should be mixed and blessed on the day of Pentecost rather than on Maundy Thursday.

On the contrary Is the use of the Church, who is governed by the Holy Ghost.
I answer that Our Lord promised His faithful (Mt 18,20) saying: "Where there are two or three gathered together in My name, there am I in the midst of them." And therefore we must hold firmly that the Church's ordinations are directed by the wisdom of Christ. And for this reason we must look upon it as certain that the rite observed by the Church, in this and the other sacraments, is appropriate.

Reply to Objection: 1. As Pope Melchiades says (Ep ad Epis. Hispan.), "these two sacraments," viz. Baptism and Confirmation, "are so closely connected that they can nowise be separated save by death intervening, nor can one be duly celebrated without the other." Consequently the same seasons are fixed for the solemn celebration of Baptism and of this sacrament. But since this sacrament is given only by bishops, who are not always present where priests are baptizing, it was necessary, as regards the common use, to defer the sacrament of Confirmation to other seasons also.
2. The sick and those in danger of death are exempt from this prohibition, as we read in the decree of the Council of Meaux. And therefore, on account of the multitude of the faithful, and on account of imminent dangers, it is allowed for this sacrament, which can be given by none but a bishop, to be given or received even by those who are not fasting: since one bishop, especially in a large diocese, would not suffice to confirm all, if he were confined to certain times. But where it can be done conveniently, it is more becoming that both giver and receiver should be fasting.
3. According to the acts of the Council of Pope Martin, "it was lawful at all times to prepare the chrism." But since solemn Baptism, for which chrism has to be used, is celebrated on Easter Eve, it was rightly decreed, that chrism should be consecrated by the bishop two days beforehand, that it may be sent to the various parts of the diocese. Moreover, this day is sufficiently appropriate to the blessing of sacramental matter, since thereon was the Eucharist instituted, to which, in a certain way, all the other sacraments are ordained, as stated above (Question [65], Article [3]).

EUCHARIST (Questions [73]-83)


We have now to consider the sacrament of the Eucharist; and first of all we treat of the sacrament itself; secondly, of its matter; thirdly, of its form; fourthly, of its effects; fifthly, of the recipients of this sacrament; sixthly, of the minister; seventhly, of the rite.

Under the first heading there are six points of inquiry:

(1) Whether the Eucharist is a sacrament?

(2) Whether it is one or several sacraments?

(3) Whether it is necessary for salvation?

(4) Its names;

(5) Its institution;

(6) Its figures.

Whether the Eucharist is a sacrament?

Objection: 1. It seems that the Eucharist is not a sacrament. For two sacraments ought not to be ordained for the same end, because every sacrament is efficacious in producing its effect. Therefore, since both Confirmation and the Eucharist are ordained for perfection, as Dionysius says (Eccl. Hier. iv), it seems that the Eucharist is not a sacrament, since Confirmation is one, as stated above (Question [65], Article [1]; Question [72], Article [1]).
2. Further, in every sacrament of the New Law, that which comes visibly under our senses causes the invisible effect of the sacrament, just as cleansing with water causes the baptismal character and spiritual cleansing, as stated above (Question [63], Article [6]; Question [66], Articles [1],3,7). But the species of bread and wine, which are the objects of our senses in this sacrament, neither produce Christ's true body, which is both reality and sacrament, nor His mystical body, which is the reality only in the Eucharist. Therefore, it seems that the Eucharist is not a sacrament of the New Law.
3. Further, sacraments of the New Law, as having matter, are perfected by the use of the matter, as Baptism is by ablution, and Confirmation by signing with chrism. If, then, the Eucharist be a sacrament, it would be perfected by the use of the matter, and not by its consecration. But this is manifestly false, because the words spoken in the consecration of the matter are the form of this sacrament, as will be shown later on (Question [78], Article [1]). Therefore the Eucharist is not a sacrament.

On the contrary It is said in the Collect [*Postcommunion "pro vivis et defunctis"]: "May this Thy Sacrament not make us deserving of punishment."
I answer that The Church's sacraments are ordained for helping man in the spiritual life. But the spiritual life is analogous to the corporeal, since corporeal things bear a resemblance to spiritual. Now it is clear that just as generation is required for corporeal life, since thereby man receives life; and growth, whereby man is brought to maturity: so likewise food is required for the preservation of life. Consequently, just as for the spiritual life there had to be Baptism, which is spiritual generation; and Confirmation, which is spiritual growth: so there needed to be the sacrament of the Eucharist, which is spiritual food.

Reply to Objection: 1. Perfection is twofold. The first lies within man himself; and he attains it by growth: such perfection belongs to Confirmation. The other is the perfection which comes to man from the addition of food, or clothing, or something of the kind; and such is the perfection befitting the Eucharist, which is the spiritual refreshment.
2. The water of Baptism does not cause any spiritual effect by reason of the water, but by reason of the power of the Holy Ghost, which power is in the water. Hence on Jn 5,4, "An angel of the Lord at certain times," etc., Chrysostom observes: "The water does not act simply as such upon the baptized, but when it receives the grace of the Holy Ghost, then it looses all sins." But the true body of Christ. bears the same relation to the species of the bread and wine, as the power of the Holy Ghost does to the water of Baptism: hence the species of the bread and wine produce no effect except from the virtue of Christ's true body.
3. A sacrament is so termed because it contains something sacred. Now a thing can be styled sacred from two causes; either absolutely, or in relation to something else. The difference between the Eucharist and other sacraments having sensible matter is that whereas the Eucharist contains something which is sacred absolutely, namely, Christ's own body; the baptismal water contains something which is sacred in relation to something else, namely, the sanctifying power: and the same holds good of chrism and such like. Consequently, the sacrament of the Eucharist is completed in the very consecration of the matter, whereas the other sacraments are completed in the application of the matter for the sanctifying of the individual. And from this follows another difference. For, in the sacrament of the Eucharist, what is both reality and sacrament is in the matter itself. but what is reality only, namely, the grace bestowed, is in the recipient; whereas in Baptism both are in the recipient, namely, the character, which is both reality and sacrament, and the grace of pardon of sins, which is reality only. And the same holds good of the other sacraments.

Whether the Eucharist is one sacrament or several?

Objection: 1. It seems that the Eucharist is not one sacrament but several, because it is said in the Collect [*Postcommunion "pro vivis et defunctis"]: "May the sacraments which we have received purify us, O Lord": and this is said on account of our receiving the Eucharist. Consequently the Eucharist is not one sacrament but several.
2. Further, it is impossible for genera to be multiplied without the species being multiplied: thus it is impossible for one man to be many animals. But, as stated above (Question [60], Article [1]), sign is the genus of sacrament. Since, then, there are more signs than one, to wit, bread and wine, it seems to follow that here must be more sacraments than one.
3. Further, this sacrament is perfected in the consecration of the matter, as stated above (Article [1], ad 3). But in this sacrament there is a double consecration of the matter. Therefore, it is a twofold sacrament.

On the contrary The Apostle says (1Co 10,17): "For we, being many, are one bread, one body, all that partake of one bread": from which it is clear that the Eucharist is the sacrament of the Church's unity. But a sacrament bears the likeness of the reality whereof it is the sacrament. Therefore the Eucharist is one sacrament.
I answer that As stated in Metaph. v, a thing is said to be one, not only from being indivisible, or continuous, but also when it is complete; thus we speak of one house, and one man. A thing is one in perfection, when it is complete through the presence of all that is needed for its end; as a man is complete by having all the members required for the operation of his soul, and a house by having all the parts needful for dwelling therein. And so this sacrament is said to be one. Because it is ordained for spiritual refreshment, which is conformed to corporeal refreshment. Now there are two things required for corporeal refreshment, namely, food, which is dry sustenance, and drink, which is wet sustenance. Consequently, two things concur for the integrity of this sacrament, to wit, spiritual food and spiritual drink, according to John: "My flesh is meat indeed, and My blood is drink indeed." Therefore, this sacrament is materially many, but formally and perfectively one.

Reply to Objection: 1. The same Collect at first employs the plural: "May the sacraments which we have received purify us"; and afterwards the singular number: "May this sacrament of Thine not make us worthy of punishment": so as to show that this sacrament is in a measure several, yet simply one.
2. The bread and wine are materially several signs, yet formally and perfectively one, inasmuch as one refreshment is prepared therefrom.
3. From the double consecration of the matter no more can be gathered than that the sacrament is several materially, as stated above.

Whether the Eucharist is necessary for salvation?

Objection: 1. It seems that this sacrament is necessary for salvation. For our Lord said (Jn 6,54): "Except you eat the flesh of the Son of Man, and drink His blood, you shall not have life in you." But Christ's flesh is eaten and His blood drunk in this sacrament. Therefore, without this sacrament man cannot have the health of spiritual life.
2. Further, this sacrament is a kind of spiritual food. But bodily food is requisite for bodily health. Therefore, also is this sacrament, for spiritual health.
3. Further, as Baptism is the sacrament of our Lord's Passion, without which there is no salvation, so also is the Eucharist. For the Apostle says (1Co 11,26): "For as often as you shall eat this bread, and drink the chalice, you shall show the death of the Lord, until He come." Consequently, as Baptism is necessary for salvation, so also is this sacrament.

On the contrary Augustine writes (Ad Bonifac. contra Pelag. I): "Nor are you to suppose that children cannot possess life, who are deprived of the body and blood of Christ."
I answer that Two things have to be considered in this sacrament, namely, the sacrament itself, and what is contained in it. Now it was stated above (Article [1], Objection [2]) that the reality of the sacrament is the unity of the mystical body, without which there can be no salvation; for there is no entering into salvation outside the Church, just as in the time of the deluge there was none outside the Ark, which denotes the Church, according to 1P 3,20-21. And it has been said above (Question [68], Article [2]), that before receiving a sacrament, the reality of the sacrament can be had through the very desire of receiving the sacrament. Accordingly, before actual reception of this sacrament, a man can obtain salvation through the desire of receiving it, just as he can before Baptism through the desire of Baptism, as stated above (Question [68], Article [2]). Yet there is a difference in two respects. First of all, because Baptism is the beginning of the spiritual life, and the door of the sacraments; whereas the Eucharist is, as it were, the consummation of the spiritual life, and the end of all the sacraments, as was observed above (Question [63], Article [6]): for by the hallowings of all the sacraments preparation is made for receiving or consecrating the Eucharist. Consequently, the reception of Baptism is necessary for starting the spiritual life, while the receiving of the Eucharist is requisite for its consummation; by partaking not indeed actually, but in desire, as an end is possessed in desire and intention. Another difference is because by Baptism a man is ordained to the Eucharist, and therefore from the fact of children being baptized, they are destined by the Church to the Eucharist; and just as they believe through the Church's faith, so they desire the Eucharist through the Church's intention, and, as a result, receive its reality. But they are not disposed for Baptism by any previous sacrament, and consequently before receiving Baptism, in no way have they Baptism in desire; but adults alone have: consequently, they cannot have the reality of the sacrament without receiving the sacrament itself. Therefore this sacrament is not necessary for salvation in the same way as Baptism is.

Reply to Objection: 1. As Augustine says, explaining Jn 6,54, "This food and this drink," namely, of His flesh and blood: "He would have us understand the fellowship of His body and members, which is the Church in His predestinated, and called, and justified, and glorified, His holy and believing ones." Hence, as he says in his Epistle to Boniface (Pseudo-Beda, in 1Co 10,17): "No one should entertain the slightest doubt, that then every one of the faithful becomes a partaker of the body and blood of Christ, when in Baptism he is made a member of Christ's body; nor is he deprived of his share in that body and chalice even though he depart from this world in the unity of Christ's body, before he eats that bread and drinks of that chalice."
2. The difference between corporeal and spiritual food lies in this, that the former is changed into the substance of the person nourished, and consequently it cannot avail for supporting life except it be partaken of; but spiritual food changes man into itself, according to that saying of Augustine (Confess. vii), that he heard the voice of Christ as it were saying to him: "Nor shalt thou change Me into thyself, as food of thy flesh, but thou shalt be changed into Me." But one can be changed into Christ, and be incorporated in Him by mental desire, even without receiving this sacrament. And consequently the comparison does not hold.
3. Baptism is the sacrament of Christ's death and Passion, according as a man is born anew in Christ in virtue of His Passion; but the Eucharist is the sacrament of Christ's Passion according as a man is made perfect in union with Christ Who suffered. Hence, as Baptism is called the sacrament of Faith, which is the foundation of the spiritual life, so the Eucharist is termed the sacrament of Charity, which is "the bond of perfection" (Col 3,14).

Whether this sacrament is suitably called by various names?

Objection: 1. It seems that this sacrament is not suitably called by various names. For names should correspond with things. But this sacrament is one, as stated above (Article [2]). Therefore, it ought not to be called by various names.
2. Further, a species is not properly denominated by what is common to the whole genus. But the Eucharist is a sacrament of the New Law; and it is common to all the sacraments for grace to be conferred by them, which the name "Eucharist" denotes, for it is the same thing as "good grace." Furthermore, all the sacraments bring us help on our journey through this present life, which is the notion conveyed by "Viaticum." Again something sacred is done in all the sacraments, which belongs to the notion of "Sacrifice"; and the faithful intercommunicate through all the sacraments, which this Greek word (Synaxis) and the Latin "Communio" express. Therefore, these names are not suitably adapted to this sacrament.
3. Further, a host [*From Latin "hostia," a victim] seems to be the same as a sacrifice. Therefore, as it is not properly called a sacrifice, so neither is it properly termed a "Host."

On the contrary is the use of these expressions by the faithful.
I answer that This sacrament has a threefold significance. one with regard to the past, inasmuch as it is commemorative of our Lord's Passion, which was a true sacrifice, as stated above (Question [48], Article [3]), and in this respect it is called a "Sacrifice."With regard to the present it has another meaning, namely, that of Ecclesiastical unity, in which men are aggregated through this Sacrament; and in this respect it is called "Communion" or (Synaxis). For Damascene says (De Fide Orth. iv) that "it is called Communion because we communicate with Christ through it, both because we partake of His flesh and Godhead, and because we communicate with and are united to one another through it."With regard to the future it has a third meaning, inasmuch as this sacrament foreshadows the Divine fruition, which shall come to pass in heaven; and according to this it is called "Viaticum," because it supplies the way of winning thither. And in this respect it is also called the "Eucharist," that is, "good grace," because "the grace of God is life everlasting" (Rm 6,23); or because it really contains Christ, Who is "full of grace."In Greek, moreover, it is called (Metalepsis), i.e. "Assumption," because, as Damascene says (De Fide Orth. iv), "we thereby assume the Godhead of the Son."

Reply to Objection: 1. There is nothing to hinder the same thing from being called by several names, according to its various properties or effects.
2. What is common to all the sacraments is attributed antonomastically to this one on account of its excellence.
3. This sacrament is called a "Sacrifice" inasmuch as it represents the Passion of Christ; but it is termed a "Host" inasmuch as it contains Christ, Who is "a host (Douay: 'sacrifice') . . . of sweetness" (Ep 5,2).

Whether the institution of this sacrament was appropriate?

Objection: 1. It seems that the institution of this sacrament was not appropriate, because as the Philosopher says (De Gener. ii): "We are nourished by the things from whence we spring." But by Baptism, 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 this sacrament as spiritual nourishment.
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 (Question [8], Articles [3],6). Therefore the institution of this sacrament should not have been postponed till the Lord's supper.
3. Further, this sacrament is called the memorial of our Lord's Passion, according to Mt 26 (Lc 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.
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 Mt 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 (Mc 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 His disciples in His proper species, He left Himself with them under the sacramental species; as the Emperor'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 Rm 3,25: "Whom God hath proposed to be a propitiation, through faith in His blood." It was necessary accordingly 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 (1Co 5,7): "Christ our Pasch is sacrificed." But its successor under the New Testament is the sacrament 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, "among sacrifices 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 Christ through Baptism, so through the Eucharist we eat Christ.
2. The Eucharist is the perfect sacrament of our Lord's Passion, as containing Christ crucified; consequently it could not be instituted before the Incarnation; but then there was room for only such sacraments as were prefigurative of the Lord's Passion.
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.
4. The institution responds to the order of intention. But the sacrament of the Eucharist, 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's Baptism; hence some were already baptized with Christ's Baptism, as we read in Jn 3,22.

Summa Th. III EN Qu.72 a.10