8:18-21 The kings of Midian must be reckoned with. As they confessed themselves guilty of murder, Gideon acted as the avenger of blood, being the next of kin to the persons slain. Little did they think to have heard of this so long after; but murder seldom goes unpunished in this life. Sins long forgotten by man, must be accounted for to God. What poor consolation in death from the hope of suffering less pain, and of dying with less disgrace than some others! yet many are more anxious on these accounts, than concerning the future judgment, and what will follow.
20. he said unto Jether his first-born, Up, and slay them—The nearest of kin was the blood-avenger; but a magistrate might order any one to do the work of the executioner; and the person selected was always of a rank equal or proportioned to that of the party doomed to suffer (1Ki 2:29). Gideon intended, then, by the order to Jether, to put an honor on his son, by employing him to slay two enemies of his country; and on the youth declining, he performed the bloody deed himself.