Ephesians 4:29 tells us, "Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen."
First Peter 3:10 declares, "For, whoever would love life and see good days must keep his tongue from evil and his lips from deceitful speech."
Sin is a condition of the heart, the mind, and “the inner man” (Romans 7:22), which is manifested in our thoughts, actions and when we swear and curse, we are giving evidence of the polluting sin in our hearts that must be confessed and repented of.
When this happens, we receive a new nature from God (2 Corinthians 5:17), our hearts are transformed, and our speech reflects the new nature God has created within us.
Ephesians 5:4
4 Neither filthiness, nor foolish talking, nor coarse jesting, which are not convenient: but rather giving of thanks
1 Corinthians 5:11
11 But now I have written unto you not to keep company, if any man that is called a brother be a fornicator, or covetous, or an idolator, """""or a railer""""", or a drunkard, or an extortioner; with such an one no not to eat.
KJV Dictionary Definition: railer railer. RA'ILER, n. One who scoffs, insults, censures or reproaches with opprobrious language.
1 Corinthians 6:9-10
9 Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind,
10 Nor thieves, nor covetous, nor drunkards, """"nor revilers""""", nor extortioners, shall inherit the kingdom of God.
KJV Dictionary Definition: revile (r?'va?l) vb
1. to use abusive or scornful language against (someone or something)
2. to address or speak of with contemptuous, abusive, or opprobrious language.
3. to speak abusively.