“Let no corrupt word proceed out of your mouth, but what is good for necessary edification, that it may impart grace to the hearers” (Ephesians 4:29).
Learning Christ and putting on the new man in true righteousness and holiness is a stark contrast from the unholy lifestyle of the old man. It thoroughly changes how you think, act, live, and talk.
At no time in His life did corrupt/unwholesome speech come out of our Lord’s mouth. No bad, rotten, or foul words ever crossed His pure lips. He never lied, blasphemed, boasted, cursed, reviled, or gossiped. His speech was always morally honorable and pleasing to God.
Jesus had pure speech because He was ever vigilant in watching over and guarding His heart to keep it pure. Those things which proceed out of the mouth come from the heart (Matthew 15:18). Therefore, to have pure speech as Christ did, you cannot have an impure heart.
The purpose of your speech is to help others improve spiritually. Therefore, it includes rebuking and reproving those who are in sin as Jesus did Peter (Matthew 16:23). It necessitates words of mercy and reassurance to the penitent (John 8:11; Luke 7:48-50). It ever seeks to speak words which are most appropriate to the circumstances (Proverbs 25:11), so that your words are a well of life (Proverbs 10:11) and grace is imparted to your hearers.