Hebrews 7:23

And they truly were many priests, because they were not suffered to continue by reason of death:

The verse means that the priests of the earthly order were many in succession because death removed them and prevented any one of them from continuing long in office. In contrast, Jesus is a priest forever after the order of Melchizedek, and His mediatorial work endures. The high priest was designed and meant to represent Christ. His priesthood does not pass to another, yield to a successor, or become superseded.

The earthly priests ministered in both apartments of the earthly sanctuary, daily in the first apartment and once a year in the most holy place to cleanse it from the sins conveyed there. They entered with the blood of an animal as an offering for sin, while Jesus ministers in both apartments of the heavenly sanctuary by the offering of His own blood. The earthly sanctuary figures the heavenly, and the particulars of the earthly work were given so that the work of Jesus in the heavenly sanctuary can be understood. The sacrifices and offerings brought to the earthly sanctuary were for laying hold of the merits of a Saviour to come.

The earthly priesthood and its sacrifices were symbols pointing to Christ and had no power to save apart from Him, and they were to continue only until the perfect Offering came. Christ's priestly work exceeds the earthly priesthood in dignity and glory, and through His mediation the sinner can approach God. By the time of Christ's first advent, men often gained the high-priestly office through ambition, bribery, or assassination rather than by divine appointment.

As the enduring Advocate and Surety in contrast to the many mortal priests, Christ is the one with whom to stand for divine light and protection. Salvation depends on standing with Him, and humanity is made complete only through union with divinity.