Deuteronomy 19:2

“But if he did not lie in wait for him, but God let him fall into his hand, then I will appoint you a place to which he may flee.

then you shall select for yourselves cities to be your cities of refuge, that the manslayer who has struck down any person unintentionally may flee there.

Then Moses set apart three cities across the Jordan to the east toward the sunrise,

“Speak to the sons of Israel, saying, ‘Designate the cities of refuge, of which I spoke to you by the hand of Moses,