The Holy Mass is called a sacrifice not because Christ is crucified again. Rather, it is called this because you and I participate in his one and eternal sacrifice ‘re-presented’ (made present again)to us in an unbloody manner. The sacrifice of the cross and the sacrifice of the Mass are numerically one, present in different modalities. There is no new sacrifice in the Holy Eucharist but a different mode of the same sacrifice. Holy Mass is not a mere recollection but rather a re-presentation of the Passion. We now participate by acts of loving devotion in that which we previously only participated in by sinfulness. In other words, our sins were present at the cross. So too by the power of the Mass are our acts of sacrificial love. The one, eternal offering is applied to diverse times and places in fulfillment of his command to “do this.”
[Fr. Matthew Kauth: The Sacraments, St. Benedict Press, 2018, p 67]