As a young man I was a horrible driver. I was a reckless, inconsiderate, and foolish driver who drove too fast and took way too many chances. Because of that, I had way too many wrecks. To this day my dad will not go anywhere with me if I’m driving. As I got older, I tried to be more careful, but bad habits are hard to break. The Bible does not have any commandments directly about driving. Driving is not even mentioned in the Bible. So while it is clear I was not deliberately breaking a known law of God, any reasonable and thinking person would recognize that what I was doing was unrighteous. It was not right to treat my fellow drivers to that type of fear and danger. It was not right to put myself at that kind of risk, and it was not right to have such total disregard for traffic laws.
What does this have to do with Gideon? While he lived, the land experienced 40 years of peace. He died at a good old age and was buried with respect in the tomb of his father. Gideon had many wives, and 70 sons. He also had a concubine in the town of Shechem with one son. There was no direct commandment forbidding polygamy, or even having a concubine at that time, so was Gideon living a life of sin in his old age? One might argue that he was missing the mark, but not transgressing a known law of God. That could lead to an argument about the definition of sin, so let’s forget sin, and change the question, “Was Gideon living righteously in his old age?”
Polygamy gives birth to all types of negative emotions including jealousy, and envy. A polygamist ends up loving one more than another and showing favoritism. Gideon’s children grew up in an atmosphere of competition, giving rise to feelings of inadequacy and animosity. Gideon’s polygamy, like my reckless driving was unrighteous.
Many things the Bible doesn’t forbid are still unrighteous.