Charles Ellicott Commentary Numbers 35:25

"and the congregation shall deliver the manslayer out of the hand of the avenger of blood, and the congregation shall restore him to his city of refuge, whither he was fled: and he shall dwell therein until the death of the high priest, who was anointed with the holy oil." — Numbers 35:25 (ASV)

And he shall abide in it until the death of the high priest. Although the death that had been caused was accidental, not intentional, nevertheless the shedding of blood demanded expiation. The manslayer was, therefore, required to remain an exile from his own home until the death of the high priest who had been anointed with the holy oil. Just as the high priest, because of the anointing with the holy oil, became qualified to act as the representative of the nation and in that capacity acted as their mediator on the great Day of Atonement, so the death of the high priest assumed a symbolic or representative character, becoming a type of the death of the great High Priest. This great High Priest, through the eternal Spirit, offered Himself without spot to God and by His death made a propitiation for the sins of the world.

Thus, just as a typical atonement was made for the sin of the Israelite manslayer by the death of the Jewish high priest, and he was then restored to the land of his possession among his brethren, so too, by the death of our High Priest, are those who have fled for refuge to lay hold on the hope set before them restored to the inheritance forfeited by sin and made joint heirs with Christ of those mansions He has gone to prepare for those who love Him.