Deuteronomy 19:7

4 This is the case of the manslayer, that shall flee there and live: whoever kills his neighbor unawares, and didn`t hate him in time past;

5 as when a man goes into the forest with his neighbor to hew wood, and his hand fetches a stroke with the ax to cut down the tree, and the head slips from the handle, and lights on his neighbor, so that he dies; he shall flee to one of these cities and live:

6 lest the avenger of blood pursue the manslayer, while his heart is hot, and overtake him, because the way is long, and strike him mortally; whereas he was not worthy of death, inasmuch as he didn`t hate him in time past.

7 Therefore I command you, saying, You shall set apart three cities for you.

8 If Yahweh your God enlarge your border, as he has sworn to your fathers, and give you all the land which he promised to give to your fathers;

9 if you shall keep all this commandment to do it, which I command you this day, to love Yahweh your God, and to walk ever in his ways; then shall you add three cities more for you, besides these three:

10 that innocent blood not be shed in the midst of your land, which Yahweh your God gives you for an inheritance, and so blood be on you.