Why does a perpetual sacrifice of Jesus exist? If Jesus sacrificed himself once for all, past present and future, why is He perpetually sacrificing Himself?
It’s important to point out that the Catholic Church does not teach Jesus offers himself over and over again in the Mass. The sacrifice of the Mass is the same sacrifice as the one Jesus offered on the cross. The only difference is the manner of offering. 2000 years ago it was offered in a bloody manner and on the altar it is offered in an unbloody manner. Paragraph 1367 of the Catechism of the Catholic Church states:
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.” “And since 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 offered in an unbloody manner … this sacrifice is truly propitiatory.”
This teaching is based on the biblical understanding that Jesus continues to offer that same sacrifice to the Father in heaven in an unbloody manner. Recall Hebrews 7:24 states that Jesus is our priest forever in the heavenly sanctuary. And according to Hebrews 5:1every priest has to have sacrifices to offer. So, what is Jesus offering as the heavenly high priest? It can’t be some other sacrifice. It must be himself–the same sacrifice offered on earth 2000 years ago. The Mass is simply the making present of that one sacrifice in the here and now.
So, if by perpetual you mean Jesus is offering himself over and over again, then you are misunderstanding the Catholic position. But if by perpetual you mean Jesus is offering the one sacrifice for the rest of eternity, then the rationale is because he is the high priest ministering in the heavenly sanctuary on our behalf.