because the manslayer must remain in his city of refuge until the death of the high priest. Only after the death of the high priest may he return to the land he owns.
28. Because he should have remained in the city of his refuge. The period of banishment is prescribed, “until the death of the high-priest,” because it would have been anything but humane that all hopes of restoration should have been cut off from the unhappy exile; and, when a new priest succeeded to reconcile the people to God, this renewal of grace was to propitiate all offenses.
Because he should have remained in the city of his refuge until the death of the high priest,.... Nothing could give him his liberty but his death; so that though this was a merciful provision made in such cases for such persons, and was a considerable benefit and privilege, yet it carried in it some appearance of a punishment; since such a person was confined...
Num 35:26-28 If he left the city of refuge before this, and the avenger of blood got hold of him, and slew him outside the borders (precincts) of the city, it was not to be reckoned to him as blood (דּם לו אין, like דּמים לו אין, Exo 22:1).
Commenting on Numbers 35:26-28