Explain the teaching: the Last Supper Mass is our ongoing Mass.
In our ongoing efforts toward growing in right understanding of our Catholic faith, the words that are used in defining and describing the truths of faith must be as clear and precise as possible. That said, in reading this request of an explanation, I must admit openly that I want to be cautious about using the terminology “Last Supper Mass” and even the word “ongoing” to describe the relationship between what Jesus Himself instituted on that Holy Thursday and Good Friday and the Mass as we know it. Accordingly, I will offer the Church’s teaching on how each celebration of Holy Mass is connected both to the Last Supper and to Jesus’ offering of Himself on Calvary, making use of the very precise words that have been handed down to us in the Church’s teaching.
In the Letter to the Hebrews we read that Jesus Christ, the true High Priest, offered Himself “once for all.” Jesus’ one-time offering of His Body and Blood in the bloody and violent manner of the cross is fruitful for all eternity, as He who died and rose is eternal. What He did once remains present and effective for all eternity (and thus, His sacrifice is never to be understood as needing to be repeated as some mistakenly claim). In His wisdom and love, Jesus willed to provide the means for His people to partake of this eternal fruitfulness and effectiveness of His saving sacrifice through the “unbloody and non-violent” manner that He instituted at the Last Supper by offering Himself in the forms of unleavened bread and wine.
Mindful of these truths of a one-time offering that is effective in all eternity, the precise language that the Church uses to describe the connection between the Mass and both the Last Supper and Calvary is as a “re-presentation” of His one-time sacrifice of Calvary, in an unbloody and non-violent manner. That is to say, every
offering of the Mass is a “making present” of the sacrifice of Christ after the manner that He left for His Church at the Last Supper – that His very offering of Himself (His Body, Blood, Soul, and Divinity) might be made present for all generations under the appearances of unleavened bread and wine until the end of time. Our participation in the Mass is thus a sharing in the one-time sacrifice, made present in the “now.” Such a great mystery of re-presentation is possible as its origin and power are God Himself, who is outside of time (or, said another way, is eternally “present”).
Thus, when the Holy Mass is offered (and yes, it remains a “sacrifice,” as it is the “sacrificial offering of Christ” that is re-presented), it is Christ Himself, through the ordained priest, who is both the offering and the effect: His Body and Blood are offered that all who faithfully partake may receive the gift of His divine life. In His
eternal nature, each Mass is thus connected to both the Last Supper and to Calvary, offering us in time the saving effects of His one-time sacrifice. In this way, what we do regularly always is an entrance into the eternal “presence” of God – whose one-time sacrifice is eternally effective.