Judges 8:20

And he said unto Jether his firstborn, Up, and slay them. But the youth drew not his sword: for he feared, because he was yet a youth.

He said unto Jether his first-born, Up, and slay them. The nearest of kin was the go'el - i:e., blood avenger; and Jether, though but little more than a boy, was the go'el of his kin, and as such the protector even of his aged father. He was his father's first-born; and that Gideon could not be a go'el is clear from Judges 4:15, where he says, "I am the least" - literally, the small one, or youngest, in my father's house. 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 (1 Kings 2:29). Gideon intended, then, by the order to Jether as the proper go'e of the family, to put an honour on his son, by employing him to slay two enemies of his country and murderers of his uncles; and on the youth declining, performed the bloody deed himself.