For Holy Thursday
The day before he suffered, our beloved Lord and Savior Jesus Christ gave to his Bride, the Church, a very precious gift, the Holy Eucharist. In these years following the Great Jubilee year 2000, a year that the Holy Father called “intensely Eucharistic” (Tertio Millennio Adveniente, 55), let us prayerfully reflect on this mystery of faith.
The Church therefore believes that at the Last Supper, Christ celebrated in a sacramental form what he was to offer in a bloody way the following day on the altar of the Cross. In that upper room what was later in Catholic theology called transubstantiation took place. The whole substance of bread was changed into the Body of Christ and the whole substance of wine was changed into the Blood of Christ (cf. Council of Trent: Decree on the Most Holy Eucharist, c. 4 and Canon 2). Christ offered himself in a sacramental way to the Eternal Father. Then he gave his Body and Blood to his Apostles so that receiving him they might be very closely united with him. And he ordered them to do this in memory of him.
This means that the Eucharistic Sacrifice is like the Sacrifice of Calvary because Christ is the offerer and the victim in both. There are, however, differences. On the Cross, Christ shed his blood. At the Eucharistic Sacrifice he does not shed his blood and does not suffer again. At Mass Christ uses the ministry of the ordained priest. On Calvary he offered himself without an instrument…the Sacrifice of the Mass bears direct relationship to the Sacrifice of Calvary. It renews–or recalls or reenacts–that Sacrifice in the sacramental forms of bread and wine.
Francis Cardinal Arinze, The Holy Eucharist