Joshua 20:2

“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.

“Speak to the sons of Israel and say to them, ‘When you cross the Jordan into the land of Canaan,

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.

‘And the cities shall be for you as a refuge from the avenger, so that the manslayer will not die until he stands before the congregation for judgment.

you shall set apart three cities for yourself in the midst of your land, which Yahweh your God gives you to possess.