Hebrews 10:24: “with one sacrifice, then, he has made perfect forever those who are purified from sin.”
1544 Everything that the priesthood of the Old Covenant prefigured finds its fulfillment in Christ Jesus, the “one mediator between God and men.” The Christian tradition considers Melchizedek, “priest of God Most High,” as a prefiguration of the priesthood of Christ, the unique “high priest after the order of Melchizedek”; “holy, blameless, unstained,” “by a single offering he has perfected for all time those who are sanctified,” that is, by the unique sacrifice of the cross.
1545 The redemptive sacrifice of Christ is unique, accomplished once for all; yet it is made present in the Eucharistic sacrifice of the Church. The same is true of the one priesthood of Christ; it is made present through the ministerial priesthood without diminishing the uniqueness of Christ’s priesthood: "Only Christ is the true priest, the others being only his ministers."
Catechism of the Catholic Church
Sections 1536-1553 of the Catechism deal specifically with the office of the New Testament priest. For a more in-depth discussion of this topic, I recommend the following:
The Priesthood Debate by Jimmy Akin:
The Office of the New Testament Priest by Jimmy Akin: