Brothers, do not slander one another. Anyone who speaks against his brother or judges him speaks against the law and judges it. When you judge the law, you are not keeping it, but sitting in judgment on it. There is only one Lawgiver and Judge, the one who is able to save and destroy. But you—who are you to judge your neighbor?This passage is really about authority. We are not to slander our brother or sit in condemnation about our brother, making decisions about his motives and reasonings... Why? Because we are not the judge!
There is only one judge. There is only one lawgiver! There is only one because THERE IS ONLY ONE! He is the only one with the power to save and the power to destroy. When we sit in condemnation, making decisions about people, we are attempting to take His authority when we don't have the authority, or for that matter, the ability.
You see, not only, should we not be judges, because there is already a judge, but also, could we not be judges because we don't have the power to save or the power to destroy.