How is the Mass the same sacrifice as that of the Cross?

A. The Mass is the same sacrifice as that of the Cross because the offering and the priest are the same--Christ Our Blessed Lord: and the ends for which the sacrifice of the Mass is offered are the same as those of the sacrifice of the Cross.

On the Cross the offering was the body and blood of Our Lord; the one who offered it was Our Lord; the reason for which He offered it was that He might atone for sin; the one to whom He offered it was His heavenly Father. Now, at Mass it is the same. The object offered is Our Lord's body and blood, the one suffering is Our Lord Himself, through the priest; it is offered for sin, and it is offered to the heavenly Father. All things are the same, except that the blood of Our Lord is not shed, and Our Lord does not die again.

Q. What are the ends for which the sacrifice of the Cross was offered?

A. The ends for which the sacrifice of the Cross was offered were: first, to honor and glorify God; second, to thank Him for all the graces bestowed on the whole world; third, to satisfy God's justice for the sins of men; fourth, to obtain all graces and blessings.

[Q: For what ends then is the Holy Sacrifice of the Mass offered?

A: The Sacrifice of the Mass is offered to God for four ends: (1) To honor Him properly, and hence it is called Latreutical; (2) To thank Him for His favors, and hence it is called Eucharistical; (3) To appease Him, make Him due satisfaction for our sins, and to help the souls in Purgatory, and hence it is called Propitiatory; (4) To obtain all the graces necessary for us, and hence it is called Impetratory. " Catechism of Pope Pius X.]

Q. Is there any difference between the sacrifice of the Cross and the sacrifice of the Mass?

A. Yes; the manner in which the sacrifice is offered is different. On the Cross Christ really shed His blood and was really slain; in the Mass there is no real shedding of blood nor real death, because Christ can die no more; but the sacrifice of the Mass, through the separate consecration of the bread and the wine, represents His death on the Cross.

Q. How should we assist at Mass?

A. We should assist at Mass with great interior recollection and piety and with every outward mark of respect and devotion. " Baltimore Catechism, on the Sacrifice of the Mass.

"They [pastors] should teach, then, in the first place, that the Eucharist was instituted by Christ for two purposes: one, that it might be the heavenly food of our souls, enabling us to support and preserve spiritual life; and the other, that the Church might have a perpetual Sacrifice, by which our sins might be expiated, and our heavenly Father, oftentimes grievously offended by our crimes, might be turned away from wrath to mercy, from the severity of just chastisement to clemency. Of this thing we may observe a type and resemblance in the Paschal lamb, which was wont to be offered and eaten by the children of Israel as a sacrament and a sacrifice..."

"We therefore confess that the Sacrifice of the Mass is and ought to be considered one and the same Sacrifice as that of the cross, for the victim is one and the same, namely, Christ our Lord, who offered Himself, once only, a bloody Sacrifice on the altar of the cross. The bloody and unbloody victim are not two, but one victim only, whose Sacrifice is daily renewed in the Eucharist, in obedience to the command of our Lord: Do this for a commemoration of me.

The priest is also one and the same, Christ the Lord; for the ministers who offer Sacrifice, consecrate the holy mysteries, not in their own person, but in that of Christ, as the words of consecration itself show, for the priest does not say: This is the body of Christ, but, This is my body; and thus, acting in the Person of Christ the Lord, he changes the substance of the bread and wine into the true substance of His body and blood.

This being the case, it must be taught without any hesitation that, as the holy Council (of Trent) has also) explained, the sacred and holy Sacrifice of the Mass is not a Sacrifice of praise and thanksgiving only, or a mere commemoration of the Sacrifice performed on the cross, but also truly a propitiatory Sacrifice, by which God is appeased and rendered propitious to us. If, therefore, with a pure heart, a lively faith, and affected with an inward sorrow for our transgressions, we immolate and offer this most holy victim, we shall, without doubt, obtain mercy from the Lord, and grace in time of need; for SO delighted is the Lord with the door of this victim that, bestowing on us the gift of grace and repentance, He pardons our sins. Hence this usual prayer of the Church: As often as the commemoration of this victim is celebrated, so often is the work of our salvation being done; that is to say, through this unbloody Sacrifice flow to us the most plenteous fruits of that bloody victim."

See, The Sacramental Sacrifice Thanksgiving, Memorial, Presence in the current catechism.

See Why Liturgy?, The Father-Source and Goal of the Liturgy, Christ's Work in the Liturgy, in the current catechism.