BiblicalInsights.net

Most people like salt added to their food to give it special taste.  This has been true for centuries.  Evidence indicates that Neolithic people of the Precucuteni Culture were boiling the salt-laden spring water through the process of briquetage to extract salt as far back as 6050 B.C. (Wikipedia).  Jesus said that if the salt has lost its savor (saltiness) it is good for nothing (Matt. 5:13).
Speech seasoned with salt is speech that has the positive influence of wholesomeness.  Col. 4:6, “Let your speech be alway with grace, seasoned with salt, that ye may know how ye ought to answer every man.”  Your speech is a reference to what you say each day.  Always with grace means with graciousness or in a kindly spirit.  Seasoned with salt refers to speech as food that is duly seasoned before it is served and thus is palatable when it is served.  Salt is the wholesomeness of what we say.  That ye may know is an infinitive of result.  How ye ought to answer every man refers to using wisdom (v. 5) and clothing our speech in graciousness and giving it a wholesome taste, we shall soon get to know just how to answer every person with whom we get into a discussion so that we can make the most of all such opportunities (Lenski, Interpretation of Colossians, p. 194).
Our speech will influence others and has the power to win them to Christ.  Our speech has a soul-winning function!
Speech Reveals Character.
Your speech is a window to your heart!  (Matthew 12:34-37).  Good men bring forth good things and evil men bring forth evil things.  When Christians bring forth evil things it is hypocrisy.  Our character has the power to win others to Christ if it exhibits godliness (I Peter 3:1).
Profane Speech From Christians Reveals Hypocrisy.
Nothing defeats the Christians’ example and influence for Christ faster than hypocrisy.  Types of profane speech that should never come from the mouth of a Christian include:  taking God’s name in vain, use of cuss words and profane language, evil speaking, and lies.  James warns against the manifestation of duplicity in the use of the tongue (James 3:9-12).  Blessing and cursing should not come forth from the same fountain.  It is hypocrisy.
Profanity reveals contempt for others.  Contempt is a mixture of anger and disgust expressed from a position of superiority.  Expressions of contempt may include:  rolling the eyes, verbal put-downs, and profanity.  Profanity denigrates, devalues and dismisses others.  Ultimately, it will damn the soul.  Offenses through speech are common, but woe to that man through whom the offense cometh!
Speech is a Test of Self-Control.
Bridle your tongue is an expression that attempts to capture the essence of self-control. Self-control is a Christian virtue (II Pet. 1:5-11).   Temperance is self-control.  We must discipline our hearts and tongues in order to manifest the moral vigor that becomes the Christian life.  This is saltiness!  Peter states that if we lack these things (moral virtues) we are blind and cannot see afar off and have forgotten that we have been purged from our old sins!
Speech Should Be Used to Hallow the World Not Profane It.
Speech influences for either good or evil.  The power of life and death is in the use of the tongue.  Speech made in wisdom, full of grace and seasoned with salt will bless.  Language has the power to reflect the holiness of God to others.  “Be ye holy for I am holy saith the Lord” (I Pet. 1:16).  Be holy even in your speech!
The problem with cussing Christians is that they reveal hypocrisy, impurity, and unholiness to a lost and dying world that cannot be won to Christ through the pursuit of the profane!