Deuteronomy 19:11-13

11But if out of hate someone lies in wait, assaults and kills a neighbor, and then flees to one of these cities, 12the killer shall be sent for by the town elders, be brought back from the city, and be handed over to the avenger of blood to die.

13Show no pity. You must purge from Israel the guilt of shedding innocent blood, so that it may go well with you.