Numbers 35:32

Moreover, ye shall take no satisfaction for him that is fled
to the city of his refuge
Though for killing a man unawares:

that he should come again to dwell in the land, until the death of the
priest;
the high priest; such a man's liberty was not to be purchased with money, nor even his life to be bought off, should he be taken without his city; a great ransom could not deliver him from the avenger, because he was guilty of this law, which so wisely and mercifully provided for him; and consequently guilty also of great ingratitude to God, as well as of a breach of his law, and of disrespect to his high priest, under whom he was protected.