פּירוש אויף במדבר 35:25

עד מות הכהן הגדול [HE SHALL ABIDE IN IT] UNTIL THE DEATH OF THE HIGH PRIEST — because he serves to cause the Shechinah to dwell in Israel and thereby prolong their days, whilst the murderer serves to make the Shechinah depart from Israel and thereby shortens the days of the living. He is therefore not worthy that he should stand before a High Priest (that he should be anywhere near a High Priest) (Sifrei Bamidbar 160:9). Another explanation why he had to remain there until the High Priest’s death: Because the High Priest should have prayed that this misfortune might never happen in Israel in his days (cf. Makkot 11a).

"Until the death of the High Priest": He who brings down the Divine Presence, etc. Another explanation is that he should have prayed, etc. It is difficult to understand the second explanation. One could say that the second explanation is more consistent, because according to the first explanation, it would not have been permissible to stand before the High Priest forever, even if another High Priest succeeded him, since one brings down the Divine Presence and the other removes it, as stated in the verse, "For your sword will be lifted over him," meaning that it is not fitting for the one who shortens (the time) to be in the position of the one who lengthens it. Therefore, the second explanation is that the High Priest was considered deficient in not praying to prevent this mishap, which is why it refers back to his death and to the days of the second High Priest.

Until the death of the high priest. And what the Torah said regarding murderers, that he shall dwell there until the death of the high priest, is because Aaron’s attribute was peace. Therefore, he should have prayed for the people of his generation that only peace and truth would prevail in his days, and that such an impure incident would not occur. Therefore, the murderer shall dwell there until the death of the high priest, and then he and his entire household will pray for the death of the high priest so that he may quickly return to his home. For this reason, it says until the death of the high priest who was anointed with the anointing oil — do we not already know that the high priest is anointed with the anointing oil? Rather, because during the days of this priest a murder took place, this murderer extinguished the lamp of God, the soul of man, and extinguished the lamp of commandment and the light of Torah. Surely this priest did not remember the holy anointing oil upon him, half [the measure of which] was 250, that is, twice the numerical value of lamp (ner = 250), for every priest needs to guard these two lamps during his days and pray for this. And since this act occurred in his days, therefore the murderer shall dwell there until the death of the high priest.