Numbers 35:14

then you shall appoint for yourselves cities to be cities of refuge for you, that the man slayer who kills any person unwittingly may flee there.

The cities shall be for your refuge from the avenger, that the man slayer not die until he stands before the congregation for judgment.

The cities which you shall give shall be for you six cities of refuge.

These six cities shall be refuge for the children of Israel, for the stranger, and for the foreigner living among them, that everyone who kills any person unwittingly may flee there.

“‘But if he struck him with an instrument of iron, so that he died, he is a murderer. The murderer shall surely be put to death.

If he struck him with a stone in the hand, by which a man may die, and he died, he is a murderer. The murderer shall surely be put to death.