Joshua 20:1 KJV

Speak to the children of Israel, saying, Appoint out for you cities of refuge, whereof I spake unto you by the hand of Moses:

That the slayer that killeth any person unawares and unwittingly may flee thither: and they shall be your refuge from the avenger of blood.

And when he that doth flee unto one of those cities shall stand at the entering of the gate of the city, and shall declare his cause in the ears of the elders of that city, they shall take him into the city unto them, and give him a place, that he may dwell among them.

And if the avenger of blood pursue after him, then they shall not deliver the slayer up into his hand; because he smote his neighbour unwittingly, and hated him not beforetime.