Dear friend,
This is a common misunderstanding and has been around since the Protestant reformation. The moment that Jesus died was an eternal moment. His sacrifice transcends time and applies to everyone who ever lived or will live. But it also remains in time as the Eucharist.
The priest does not offer a new sacrifice. Jesus died only once. But because Jesus gave His priests the power to change bread and wine into His very body and blood, they are able to offer, in the presence of the assembled Christian community today, the same body and blood that was sacrificed on Calvary.
The Catechism of the Catholic Church states: "At the Last Supper, on the night he was betrayed, our Savior instituted the Eucharistic sacrifice of his Body and Blood. This he did in order to perpetuate the sacrifice of the cross throughout the ages until he should come again, and so to entrust to his beloved Spouse, the Church, a memorial of his death and resurrection: a sacrament of love, a sign of unity, a bond of charity, a Paschal banquet ‘in which Christ is consumed, the mind is filled with grace, and a pledge of future glory is given to us.’” (#1323)
vatican.va/archive/ccc_css/archive/catechism/p2s2c1a3.htm
St. Thomas Aquinas wrote: “It was to impress the vastness of this love more firmly upon the hearts of the faithful that our Lord instituted this sacrament at the Last Supper. As he was on the point of leaving the world to go to the Father, after celebrating the Passover with his disciples, he left it as a perpetual memorial of his passion. It was the fulfillment of ancient figures and the greatest of all his miracles, while for those who were to experience the sorrow of his departure, it was destined to be a unique and abiding consolation." See:
agapebiblestudy.com/documents/St.%20Thomas%20Aquinas%20on%20the%20Feast%20of%20Corpus%20Christi.htm
When the Protestant reformers removed the notion of sacrifice from their eucharistic celebrations, they began to see the eucharist in merely symbolic terms only. This has to be the greatest tragedy of Protestantism.
Fr. Vincent Serpa, O.P.
