Christ offered Himself once for all on the Cross. He said,
"It is finished!" (Jn 19:30). The Eucharist does
not repeat this sacrifice, but re-presents it to the Father.
The sacrifice that was accomplished on Calvary is offered
again in each Mass. It can be offered now only because "it
is finished," perfected, "a perfect offering."
"In the Eucharist Christ gives us the very body which
He gave up for us on the Cross, the very blood which He 'poured
out for many for the forgiveness of sins' " (Mt 26:28;
CCC 1365). We know this is true because Christ said so:
"This is my body which is given for you," and "This
cup which is poured out for you is the new covenant in my
blood" (Lk 22:19-20).
The Eucharist is not merely an image or symbol of Christ's
sacrifice; it is Christ's sacrifice. "The sacrifice of
Christ and the sacrifice of the Eucharist are one single sacrifice:
'The victim is one and the same: the same [Christ] now offers
through the ministry of priests, who then offered Himself
on the Cross; only the manner of offering is different.' '
. . . in the Mass, the same Christ who offered Himself once
in a bloody manner on the altar of the Cross is contained
and is offered in an unbloody manner . . . " (CCC 1367)
Christ on the Cross of Calvary 2000 years ago and Christ
on the altar of your local Catholic church today are the same
person. The Christ we meet today in the Mass is the Christ
of history, for He is "Jesus Christ; the same yesterday,
today, and forever" (Heb 13:8). Christ is not divided
Christ is also not divided by space or limited by matter.
"Christ is present whole and entire in each of the species
[consecrated bread and wine] and whole and entire in each
of their parts, in such a way that the breaking of the bread
does not divide Christ" (CCC 1377).
The practical consequence of this fact is that we can and
should have the same attitude to the Eucharist that we would
have to Christ Himself if He were visibly present as He was
to His Apostles: the same attitude we would have had if we
were standing under the Cross as He was offering His life
blood for our salvation.