Numbers 35:23

“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.

“Now this is the case of the manslayer who may flee there and live: when he strikes down his friend without premeditation, not hating him previously—

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

These were the appointed cities for all the sons of Israel and for the sojourner who sojourns among them, that whoever strikes down any person unintentionally may flee there and not die by the hand of the avenger of blood until he stands before the congregation.