The manner in which the sacrifice is offered is different: on the cross Christ shed His blood and was put to death, while in the Mass there is no new immolation of the Victim, but only a new offering. On the cross Christ gained merit and satisfied for us, while in the Mass He applies to us the merits and satisfaction of His death on the cross.
1. Christ was immolated on Calvary, once and for all; He is now in glory, and can die no more. How then can we say that He is continually sacrificed on our altars? Because, as we just explained, Christ the Victim of Calvary is offered anew.
It is clear that the Mass is a unique kind of sacrifice–a sacramental sacrifice, essentially related to the Cross and depending on it. It is on the Cross that Christ became the Victim of salvation; now He is glorified, but as the Victim who has offered Himself, has been accepted, and can now apply the merits of His sacrifice.
2. The sacrifice of the Cross is the fountain of all grace and salvation. The Mass applies to us the power and merit of that sacrifice.
The sacrifice of the Cross is all-sufficient. The Mass adds nothing to it, but unfolds its riches, it brings Calvary within the reach of all men in every clime and age, in order that all men may unite themselves with it and draw upon its infinite treasures.
3. The sacrifice on Calvary was offered up by Christ for us; while at Mass He offers Himself through us.
By changing our gifts into His body and blood, Christ puts, as it were, His precious sacrifice into our hands that we may present it to the heavenly Father. In this act He “appears before the face of God on our behalf” (Hebrew 9:24).
By offering, we appropriate the treasures of Christ’s sacrifice. But if our offering is sincere, it expresses our own interior self-oblation to God. Thus the Mass becomes the oblation of the whole Mystical Body, the Church offering herself through and with Christ, her Head and Saviour. Thereby she draws upon the treasures of the Cross, in proportion to the fervour of her offering.
Thus the Mass is the sacrifice of the Cross communicated to the Church.