The avenger of blood is to put the murderer to death; when he finds him, he is to kill him.

Genesis 4:14
Behold, this day You have driven me from the face of the earth, and from Your face I will be hidden; I will be a fugitive and a wanderer on the earth, and whoever finds me will kill me."

Numbers 35:18
If anyone has in his hand a deadly object of wood, and he strikes and kills another, he is a murderer; the murderer must surely be put to death.

Numbers 35:20
Likewise, if anyone maliciously pushes another or intentionally throws an object at him and kills him,

2 Samuel 14:7
Now the whole clan has risen up against your maidservant and said, 'Hand over the one who struck down his brother, that we may put him to death for the life of the brother whom he killed. Then we will cut off the heir as well!' So they would extinguish my one remaining ember by not preserving my husband's name or posterity on the earth."

2 Samuel 14:11
"Please," she replied, "may the king invoke the LORD your God to prevent the avenger of blood from increasing the devastation, so that my son may not be destroyed!" "As surely as the LORD lives," he vowed, "not a hair of your son's head will fall to the ground."

The revenger of blood himself shall slay the murderer: when he meets him, he shall slay him.