Yoshua 20 : 3 Joshua chapter 20 verse 3

ili kwamba mwenye kuua mtu, aliyemwua mtu awaye yote pasipo kukusudia, na pasipo kujua, apate kukimbilia kuko; nayo itakuwa ni mahali pa kukimbilia kwenu, kumkimbia huyo ajilipizaye kisasi cha damu.
soma Mlango wa 20

that the manslayer who kills any person unwittingly [and] unawares may flee there: and they shall be to you for a refuge from the avenger of blood.