The sacrament of Holy Orders is when the mission entrusted by Christ to his apostles continues to be exercised in the Church until the end of time. This sacrament was prefigured in the Old Covenant in the service of the Levites, in the priesthood of Aaron, and in the institution of the seventy “Elders” (Numbers 11:25). These prefigurations find their fulfillment in Christ Jesus who by the sacrifice of the cross is the “one mediator between God and man” (1 Timothy 2:5), the “High Priest according to the order of Melchizedek” (Hebrews 5:10). The one priesthood of Christ is made present in the ministerial priesthood. “Only Christ is the true priest, the others being only his ministers.” (Saint Thomas Aquinas)