Ven. PIUS XII : The august sacrifice of the altar, then, is no mere empty commemoration of the passion and death of Jesus Christ, but a true and proper act of sacrifice

Ven. PIUS XII : The august sacrifice of the altar, then, is no mere empty commemoration of the passion and death of Jesus Christ, but a true and proper act of sacrifice, whereby the High Priest by an unbloody immolation offers Himself a most acceptable victim to the Eternal Father, as He did upon the cross. "It is one and the same victim; the same person now offers it by the ministry of His priests, who then offered Himself on the cross, the manner of offering alone being different.

MEDIATOR DEI

ENCYCLICAL OF POPE PIUS XII
ON THE SACRED LITURGY

66. The mystery of the most Holy Eucharist which Christ, the High Priest instituted, and which He commands to be continually renewed in the Church by His ministers, is the culmination and center, as it were, of the Christian religion. We consider it opportune in speaking about the crowning act of the sacred liturgy, to delay for a little while and call your attention, Venerable Brethren, to this most important subject.

67. Christ the Lord, "Eternal Priest according to the order of Melchisedech,"[56] "loving His own who were of the world,"[57] "at the last supper, on the night He was betrayed, wishing to leave His beloved Spouse, the Church, a visible sacrifice such as the nature of men requires, that would re-present the bloody sacrifice offered once on the cross, and perpetuate its memory to the end of time, and whose salutary virtue might be applied in remitting those sins which we daily commit, . . . offered His body and blood under the species of bread and wine to God the Father, and under the same species allowed the apostles, whom he at that time constituted the priests of the New Testament, to partake thereof; commanding them and their successors in the priesthood to make the same offering."[58]

68. The august sacrifice of the altar, then, is no mere empty commemoration of the passion and death of Jesus Christ, but a true and proper act of sacrifice, whereby the High Priest by an unbloody immolation offers Himself a most acceptable victim to the Eternal Father, as He did upon the cross. "It is one and the same victim; the same person now offers it by the ministry of His priests, who then offered Himself on the cross, the manner of offering alone being different."[59]

69. The priest is the same, Jesus Christ, whose sacred Person His minister represents. Now the minister, by reason of the sacerdotal consecration which he has received, is made like to the High Priest and possesses the power of performing actions in virtue of Christ's very person.[60] Wherefore in his priestly activity he in a certain manner "lends his tongue, and gives his hand" to Christ.[61]