As Christians we take for granted that Christ’s death on the cross is rightly understood as a sacrifice, and also the fulfilment of all the Old Testament sacrifices. But if we take a step back from what we simply take for granted, how is it that Christians came to this understanding? How did the disciples come to see that the death of Christ on the cross was more than the atrocious act of sentencing an innocent man to an ignominious death? What exactly is it that makes Christ’s death a sacrifice as opposed to an execution of an innocent man?
Obviously, there are many things that we could point to showing that the death of Jesus was more than just an execution; but the most evident would have to be the Last Supper. It was during the Last Supper that our Lord Jesus Christ, as the High Priest after the Order of Melchisdec (Heb 6:20), made an offering of bread and wine (Gen 14:18). But that was not where it stopped, because it was in this offering that He also gave Himself when He changed the bread and wine into His Precious Body and Blood when He said “This is My Body...This is My Blood...”.
But stepping back again from what we always take for granted, how is the Last Supper actually connected to Calvary? As Catholics we believe that the Last Supper CANNOT be separated from Calvary. And this is not based on a theological hypothesis...but on a real fact that is easy to miss if we don’t have an understanding of the Passover liturgy, which was the basis and context of the Lord’s Supper.
During the course of the Passover meal, 4 cups of wine were drunk. The cup which the Lord consecrated was the third cup, the cup of blessing (cf. 1 Cor 10:16), which was drunk after the eating of the Passover meal.
In the usual Passover meal, the liturgy would end with the drinking of the 4th cup of wine and the singing of the Great Hallel. What is interesting, and often overlooked, is that in the Last Supper our Lord and His disciples sang the Great Hallel (Matt 26:30), but they did not drink the 4th cup. Instead, our Lord said that He would not drink the fruit of the vine until He would drink it in the kingdom of God (Matt 26:29; Mk 14:25). And so it was that our Lord never actually concluded the Passover liturgy during the course of the Last Supper. This means that for our Lord and His disciples, the Passover liturgy was still continuing when they had left the Upper Room. It is this 4th cup that our Lord is likely referring to when He said “Let this cup pass from me...” (Matt 26:39).
In accordance with His words in Matt 26:29, our Lord refused to drink the wine that was mixed with gall which was offered to Him before He was nailed to the cross (Matt 27:34). But, when the time had come for Him to finally give up His life, He did drink of the fruit of the vine (Matt 27:48). St. John tells us that when He had received the wine (which would now be the 4th cup of the Passover meal), our Lord said “It is finished” (Jn 19:30). And with these words our Lord had completed the Passover meal of the Last Supper by offering Himself as the sacrificial Passover Lamb.
Here we see that the Last Supper of Jesus cannot be separated from Calvary. And because the Mass is the perpetual celebration of the Last Supper, it too cannot be separated from Calvary. This is why we as Catholics believe that every Mass is a sacrifice – in every Mass time is transcended and we take part in the Last Supper of Jesus Christ and the sacrifice of Himself on Calvary. And so, in the words of St. Paul “our paschal lamb, Christ, has been sacrificed. Therefore, let us celebrate the festival...” (1 Cor 5:7-8) always giving thanks to God that He has graciously given us His Son as the Passover Lamb who takes away our sins, and not ours only but also the sins of the world (Jn 1:29; 1 Jn 2:2).