What does Ephesians 4:29 mean?

Paul transitions from a contrast between stealing and hard work (Ephesians 4:28) to contrasting corrupting speech with encouraging speech. In both cases, his intent is to explain how Christians need to make a conscious effort to live differently than in our pre-salvation days. Just as stealing is associated with unbelievers, so also corrupting talk is associated with those who do not know Christ.

Interestingly, Paul specifically indicates that we do indeed have control over what we say: "Let no corrupting talk come out of your mouths." This contradicts the common excuse of "I couldn't help saying it." According to the Bible, we are accountable for the words we use (Matthew 12:36). Only a tiny proportion of people suffer from medical conditions which interfere with control of vocabulary. And, even such people can be expected to use whatever control they have, as much as they can. Christians do have control of our words, which are a powerful influence in how the world perceives us.

Instead of using "corrupting" or negative talk, Paul provides two guidelines for how to speak. First, we are to speak in beneficial ways about meaningful things. Second, we are to speak in ways appropriate to the situation we are in. What might be completely acceptable in one circumstance might be rude or unkind in another. The goal is to show grace to those who are listening to our words. We are not supposed to prioritize our own feelings, but make it our intent to help others through our words.