Catechism of the Catholic Church
“The sacrifice of Christ and the sacrifice of the Eucharist are one single sacrifice: ‘The victim is one and the same: the same now offers through the ministry of priests, who then offered himself on the cross; only the manner of offering is different.’ ‘In this divine sacrifice which is celebrated 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.’”
Source: Catechism of the Catholic Church #1367