Numbers 35:19

35:19 The avenger ¹  of blood himself must kill the murderer; when he meets him, he must kill him.

Numbers 35:27

35:27 and the avenger of blood finds him outside the borders of the town of refuge, and the avenger of blood kills the slayer, he will not be guilty of blood,

[35:19]  ¹ tn The participle גֹּאֵל (go’el) is the one who protects the family by seeking vengeance for a crime. This is the same verb used for levirate marriages and other related customs.