Ephesians 4:29: Well Worded
Ephesians 4:29: Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear. 
We easily see the “do not” in this verse, but there is much more than a negative. Paul commands believers to “edify” each other, which is “to carry [each other] forward” using words of “grace, comfort, advice, and everything that aids the salvation of the soul.” 
Imagine how different life would be if words were aimed at benefitting souls. No generic well-wishing or simplistic sympathies, but genuine, timely communication pointing people to Christ. How do we know Paul wants people to see Christ? The best way to give grace and build someone up is to be used by God to help make Christ the centerpiece of their life.  Further, Christ alone had perfect speech,  the speech we should emulate.  Accordingly, if we want eternally meaningful interactions, we must speak in ways that highlight and “imitate” Christ.  Christians: are our words life giving or life taking? Christ-less hearts (in people who have not trusted Christ to forgive their sins) communicate corruption rather than grace. 
 The Holy Bible: English Standard Version. (Wheaton, IL: Standard Bible Society, 2016). Logos Bible Software. All Scripture References will be ESV unless noted otherwise.
 John Calvin. Commentaries on the Epistles of Paul to the Galatians and Ephesians. Trans. William Pringle. (Grand Rapids, MI: Baker Book House Co, 1981), 300.
 John 3:16-17; Romans 6:23; Ephesians 1:3-6, 2:1-10; 1 John 4:7-21.
 2 Corinthians 5:21; 1 John 3:5, 3:8.
 Ephesians 5:4; Colossians 3:8; 3:16; 4:6, 1 Thessalonians 5:11.
 1 Corinthians 11:1.
 Matthew 12:34.