The Torah Text
The Torah describes laws around cities of refuge, where someone who accidentally kills someone can flee and be safe from blood revenge. The person seeking refuge is then restricted to that city until the high priest dies.
Ibn Ezra’s Teaching
עד מות. יש אומר עד מות עד חפוש וכמוהו תמות חכמה ולא אמרו כלום כי עמכם תמות חכמה הוא כמשמעו וגם כן עד מות הכהן הגדול כי הוא יכפר בעד ישראל וזה המאורע אירע בימיו
Numbers 35:25 THEREIN UNTIL THE DEATH OF THE HIGH PRIEST. Some say that the meaning of until the death of is, until the investigation of (meaning, until the high priest investigates the death of the victim). They compare it to, And wisdom shall die with you (Job 12:2). However, what they say is worthless. For And wisdom shall die with you means exactly what it says, as does until the death of the high priest. For the high priest atones on behalf of Israel, and this incident happened during his lifetime. (Translation adapted from Strickman and Silver)
Reflections for the Path
Ibn Ezra suggests that while the person is restricted from movement, this is not about him, but rather about the high priest, who must constantly be reminded of his failure to establish peacefulness and to pray for forgiveness from God for the bloodshed.