Luther's explanation of the 8th commandment notes that we should not tell lies about our neighbor, slander him, hurt his reputation, but speak well of him, and explain everything in the kindest way.
James the brother of Jesus has some pointed words about how we use our tongues as well when he writes, "If anyone thinks himself to be religious, and yet does not bridle his tongue but deceives his own heart, this man’s religion is worthless" (James 1:26 NASB).
It behooves us to test our tongues in light of what Luther and James write. What should be our guiding principles? Consider these 5 tests:
1. Would I say it publicly? Luther puts it this way when someone states, "'Why shouldn't I speak if it is the truth?' I reply, 'Why don't you bring it before the regular courts?' 'Oh, I cannot prove it publicly; I might be called a liar and sent away in disgrace.'
Ah, now do you smell the roast? If you do not trust yourself to make your charges before the proper authorities, then hold your tongue...when you repeat a story that you cannot prove, even if it is true, you appear as a liar" (Luther on the 8th Commandment, Large Catechism).
2. Does it accord with the Golden Rule, "Do unto others as you would have them do unto you"?
3. Would you write down your accusations and sign your name?
4. If something is troubling you, did you speak directly to the person who offended you? If it isn't worth talking to the offender about then it isn't worth talking about it to others (gossip). See Matthew 18:15.
James writes that, "No one can tame the tongue; it is a restless evil and full of deadly poison" (James 3:8 NASB). That means that all humanity, and every Christian, has failed to use the tongue as it should be used.
Sometimes we may avoid speaking hard truths for the sake of an easy life. Other times we speak harsh words that are of the flesh not of the Spirit. We fail in the proper use of words. But God gives into our mouths and on our tongues the cleansing body and blood of Jesus in with and under the bread and the wine. Jesus touches our mouths and in faith we are forgiven. Tongues set on fire by Hell receive the most holy and heavenly of gifts and we are cleansed.
Dear God, thank you for your wonderful, beautiful, merciful, words of forgiveness. You have taught us that the tongue can be set on fire by Hell or used to edify the body of Christ. We confess that we have not used our tongues as we aught. Have mercy on us Lord, and give us the grace to pour forth speech filled with truth and love. Amen.
New American Standard Bible : 1995 update. 1995 (Jas 1:26). LaHabra, CA: The Lockman Foundation.