God's commandments, though they are often terse, are remarkably broad in their application. We see this in the case law, the application of the Ten Commandments, found throughout the Pentateuch (Genesis-Deuteronomy). For example, consider the rule that merchants must employ just weights and measures (Lev. 19:36). Fallen human beings regularly attempt to make a little extra money from what they are selling by lying to others. When merchants use false weights and measures, buyers think they are getting more of a specific good or service than they actually receive. Plainly, this constitutes theft—the merchant steals from the buyer when he provides a lesser good or service than what was purchased. However, false weights and measures also violate the ninth commandment, which emphasizes our Creator's demand that we tell the truth in all of our relationships.
The ninth commandment, as revealed in today's passage, deals most explicitly with court proceedings. Our God condemns those who would condemn the innocent and acquit the wicked (Prov. 17:15), and those who bear false witness in court give testimony that may convict a person who has committed no crime or set free a true criminal. In such situations, telling the truth can be literally a matter of life or death. False testimony in capital cases can lead to the execution of people who are not guilty of murder. The matter is so serious that in ancient Israel, those who committed perjury received the penalty that would have been inflicted upon the accused if he had been found guilty (Deut. 19:15-21). If one falsely accused a person of a capital crime, the witness would receive the death penalty.
In the ninth commandment, we see how much the Lord prizes the truth. That He prizes the truth should not surprise us, for He is truth itself (John 14:6). Thus, we must strive to be scrupulously honest in all of our dealings with one another. Moreover, the ninth commandment prohibits inflicting unjust harm with our tongues. Gossip and slander come under the scope of this law's concern. Paul includes gossip as one of the manifestations of our depravity (Rom. 1:29), and we are warned again and again about repeating things we have heard about other people when we are not sure of their veracity or when repeating them serves no purpose but to titillate. Finally, we may not besmirch our neighbor's good name or tarnish his reputation by lying about his character and deeds (Lev. 19:16).
Although we tolerate slander all too often, our Lord takes it very seriously. In fact, those who slander impenitently reveal a lack of saving faith in their hearts, and God says He will destroy them (Ps. 101:5). We commonly hear slander and gossip in the church about pastors, other Christian leaders, and fellow believers. We are responsible not to initiate such things and not to repeat them when others tell these things to us.