Numbers 35:19 (BSB)

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

From Numbers 35. Also in the ESV.

Commentary on Numbers 35:19

• John Calvin (Reformed), Calvin's Commentaries on Numbers 35:19: 19. The revenger “Propinquus sanguinis.” — Lat. of blood himself. When God commanded that murderers should suffer death, He required that they should be condemned by the judges after due trial; but it seems to savor somewhat of barbarism, that he should now permit the relative of the dead man to take vengeance; for it is a very bad precedent to give the power of...
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Numbers 35:19: The revenger of blood himself shall slay the murderer,.... Not only shall have power to do it, but, as it seems, should be obliged to do it; be the executioner of the murderer; but not before his case has been heard, examined, tried, and judged; wherefore the Targum of Jonathan adds,"in judgment,''that is, as Onkelos explains it,"when he is condemned by judgment,''the court of judicature...
• Adam Clarke (Methodist), Clarke's Commentary on the Bible on Numbers 35:19: The revenger of blood - גאל הדם goel haddam, the redeemer of blood; the next in blood to him who was slain. See on Num 35:12 (note).
• Keil & Delitzsch (Lutheran), Biblical Commentary on the Old Testament on Numbers 35:19: Num 35:19 The avenger of blood could put him to death, when he hit upon him, i.e., whenever and wherever he met with him.