From: Mark 14:12-16, 22-26
The Last Supper
 And on the first day of Unleavened Bread, when they sacrificed the passover lamb, his disciples said to him (Jesus), "Where will you have us go and prepare for you to eat the passover?"  And he sent two of his disciples, and said to them, "Go into the city, and a man carrying a jar of water will meet you; follow him,  and wherever he enters, say to the householder, 'The Teacher says, where is my guest room, where I am to eat the passover with my disciples?'  And he will show you a large upper room furnished and ready; there prepare for us."  And the disciples set out and went to the city, and found it as he had told them; and they prepared the passover.
The Institution of the Eucharist
 And as they were eating, he took bread, and blessed, and broke it, and gave it to them, and said, "Take; this is my body."  And he took a cup, and when he had given thanks he gave it to them, and they all drank of it.  And he said to them, "This is my blood of the covenant, which is poured out for many.  Truly, I say to you, I shall not drink again of the fruit of the vine until that day when I drink it new in the kingdom of God."
The Disciples Will Abandon Jesus
 And when they had sung a hymn, they went out to the Mount of
12-16. At first sight our Lord's behavior described here seems quite out of character. However, if we think about it, it is quite consistent: probably Jesus wanted to avoid Judas knowing in advance the exact place where the Supper will be held, to prevent him notifying the Sanhedrin. And so God's plans for that memorable night of Holy Thursday were fulfilled: Judas was unable to advise the Sanhedrin where they could find Jesus until after the celebration of the passover meal (during which Judas left the Cenacle): cf. Jn 13:30.
St Mark describes in more detail than the other evangelists the place where the meal took place: he says it was a large, well-appointed room--a dignified place. There is an ancient Christian tradition that the house of the Cenacle was owned by Mary the mother of St Mark, to whom, it seems, the Garden of Olives also belonged.
22. The word "this" does not refer to the act of breaking the bread but to the "thing" which Jesus gives his disciples, that is, something which looked like bread and which was no longer bread but the body of Christ. "This is my body. That is to say, what I am giving you now and what you are taking is my body. For the bread is not only a symbol of the body of Christ; it becomes his very body, as the Lord has said: the bread which I shall give for the life of the world is my flesh. Therefore, the Lord conserves the appearances of bread and wine but changes the bread and wine into the reality of his flesh and his blood" (Theophylact, "Enarratio in Evangelium Marci, in loc."). Therefore, any interpretation in the direction of symbolism or metaphor does not fit the meaning of the text. The same applies to the "This is my blood" (v. 24). on the realism of these expressions, cf. first part of note on Mt 26:26-29.
24. The words of consecration of the chalice clearly show that the Eucharist is a sacrifice: the blood of Christ is poured out, sealing the new and definitive Covenant of God with men. This Covenant remains sealed forever by the sacrifice of Christ on the cross, in which Jesus is both Priest and Victim. The Church has defined this truth in these words: "If anyone says that in the Mass a true and proper sacrifice is not offered to God, or that to be offered is nothing else but that Christ is given us to eat, let him be anathema" (Council of Trent, "De S. Missae sacrificio", chap. 1, can. 1).
These words pronounced over the chalice must have been very revealing for the Apostles, because they show that the sacrifices of the Old Covenant were in fact a preparation for and anticipation of Christ's sacrifice. The Apostles were able to grasp that the Covenant of Sinai and the various sacrifices of the temple were merely an imperfect pre-figurement of the definitive sacrifice and definitive Covenant, which would take place on the cross and which they were anticipating in this Supper.
A clear explanation of the sacrificial character of the Eucharist can be found in the inspired text in chapters 8 and 9 of the Letter to the Hebrews. Similarly, the best preparation for understanding the real presence and the Eucharist as food for the soul is a reading of chapter 6 of the Gospel of St John.
In the Last Supper, then, Christ already offered himself voluntarily to his Father as a victim to be sacrificed. The Supper and the Mass constitute with the Cross one and the same unique and perfect sacrifice, for in all these cases the victim offered is the same--Christ; and the priest is the same--Christ. The only difference is that the Supper, which takes place prior to the Cross, anticipates the Lord's Death in an unbloody way and offers a victim soon to be immolated whereas the Mass offers, also in an unbloody manner, the victim already immolated on the cross, a victim who exists forever in heaven.
25. After instituting the Holy Eucharist, our Lord extends the Last Supper in intimate conversation with his disciples, speaking to them once more about his imminent death (cf. Jn, chap. 13-17). His farewell saddens the Apostles, but he promises that the day will come when he will meet with them again, when the Kingdom of God will have come in all its fullness: he is referring to the beatific life in heaven, so often compared to a banquet. Then there will be no need of earthly food or drink; instead there will be a new wine (cf. Is 25:6). Definitively, after the Resurrection, the Apostles and all the saints will be able to share the delight of being with Jesus.
The fact that St Mark brings in these words after the institution of the Eucharist indicates in some way that the Eucharist is an anticipation here on earth of possession of God in eternal blessedness, where God will be everything to everyone (cf. 1 Cor 15:28). "At the Last Supper," Vatican II teaches, "on the night he was betrayed, our Savior instituted the eucharistic sacrifice of his body and blood. This he did in order to perpetuate the sacrifice of the Cross throughout the ages until he should come again, and so to entrust to his beloved Spouse, the Church, a memorial of his death and resurrection: a sacrament of love, a sign of unity, a bond of charity, a paschal banquet in which Christ is consumed, the mind is filled with grace, and a pledge of future glory is given to us" ("Sacrosanctum Concilium", 47).
26. "When they had sung a hymn": it was a custom at the passover meal to recite prayers, called "Hallel", which included Psalms 113 to 118; the last part was recited at the end of the meal.
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.