Actually, the stated setting of the ninth commandment is the legal trial. It says, “You shall not give false testimony against your neighbor” (Exodus 20:16). Some applications of this law are found in Exodus 23:1,7 where warning is given against agreeing with the wicked to give false testimony in a case, or being partial to the poor in their disputes, all for the purpose of unlawful gain (stealing, bribery). In Deuteronomy 19:16-21 the principle is laid down that a false witness will receive the penalty the innocent party would have received if pronounced guilty because of the liar’s false testimony.
But the application of this law goes beyond the courtroom. The need for honesty in all our dealings is a natural implication of the ninth commandment. It is the basis for the Old Testament laws regarding oaths and vows (Numbers 30, for example). Vows are made to one another, but they are made to the Lord, also, and must not be broken.
For relationships in the Body of Christ, honesty is essential. “Therefore each of you must put off falsehood and speak truthfully to his neighbor, for we are all members of one body,” (Ephesians 4:25). “Do not lie to each other, since you have taken off your old self with its practices and have put on the new self, which is being renewed in knowledge in the image of its Creator,” (Colossians 3:9,10).
There do seem to be situations in which people are not obligated to tell the truth. When Rahab protected Israelite spies by lying about their having left her place, it was deemed a commendable thing (Joshua 2). When David pretended to be insane to escape the threat of a foreign enemy a psalm was written about it (1 Samuel 21:10-15; Psalm 34). If someone broke into your house and asked you where your children were, would you be obligated to tell him the truth?
Lying is as old as the devil. He lied to our parents and Jesus calls him the “father of lies” (John 8:44). Lying is a tool to manipulate our or another’s situation. It is a denial of truth’s ability to make its way in life. But truth is God’s tool for successful and happy living. Failure to tell the truth destroys trust, a key ingredient for any relationship. Telling the truth to another demonstrates respect. Even withholding truth from another suggests that that person cannot be trusted with it. Such disrespect and deceit is not consistent with the fact that we have laid aside the old self, nor is it worthy of brothers and sisters in Christ.