Be not a witness against your neighbor without cause,
and do not deceive with your lips.
Do not say, “I will do to him as he has done to me;
I will pay the man back for what he has done.”
If you have ever been the subject of slander and libel, you know how terrible it can make you feel, as your reputation has been smeared and it can be difficult to recover. Even if the lie has been exposed and your name is cleared, it can leave some wondering if there was any truth to the matter. Sometimes those who commit such a sin think they are doing so to uphold some “just” cause or to correct what they perceive as something that was not done correctly, orderly, or appropriately. They feel justified in doing so. However, verse 29 warns us not to say, "I will pay the man back for what he has done."
So even if someone has wronged you, that does not justify speaking deceitfully about him. Rather, "Repay no one evil for evil, but give thought to do what is honorable in the sight of all." Also, "Never avenge yourselves, but leave it to the wrath of God…." "Do not be overcome by evil, but overcome evil with good" (Romans 12:17, 19, 21). Speaking deceitfully against someone and then being found out will only bring upon yourself shame and disgrace, and make you a person whom others will never trust with any confidence.
Gossip is another way of committing this same error, as it destroys people’s lives, separates close friends (Proverbs 16:28), betrays a confidence (Proverbs 11:13; 20:19) and creates division in the Body of Christ (2 Corinthians 12:20). Another proverb describes the damage like this: "A man who bears false witness against his neighbor is like a war club, or a sword, or a sharp arrow" (Proverbs 25:18). King David also compares the tongue to doing the damage of a sword or arrows (Psalm 57:4; 64:3-4). This breaking of the ninth commandment (Exodus 20:16) brings you under condemnation from God’s wrath. As David prophesied, "You destroy those who speak lies; the LORD abhors the bloodthirsty and deceitful man" (Psalm 5:6).
Yet, in Christ, in whom no deceit was found, we can find forgiveness, for he bore our sin upon himself (Isaiah 53:4-6; 9). Those found in him are no longer under condemnation (Romans 8:1). From now on we should always speak the truth in love. "Let brotherly love continue" (Hebrews 13:1). "Therefore, having put away falsehood, let each one of you speak the truth with his neighbor, for we are members one of another" (Ephesians 4:25).