Numbers 35:19

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

Numbers 35:21

35:21 or with enmity he strikes him with his hand and he dies, the one who struck him must surely be put to death, for he is a murderer. The avenger of blood must kill the murderer when he meets him.

[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.