You’ve Got Questions: What’s the Problem With Cussing?
The Scriptures explicitly command against swearing, cursing (cussing), or even unwholesome language. It is definitely a sin—the apostle Paul writes in 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.” Similarly, Peter writes, “Whoever desires to love life and see good days, let him keep his tongue from evil and his lips from speaking deceit” (1 Peter 3:10, Peter quoting from Psalm 34:12-16). James 3:9-12 summarizes the issue: “With it [the tongue] we bless our Lord and Father, and with it we curse people who are made in the likeness of God. From the same mouth come blessing and cursing. My brothers, these things ought not to be so. Does a spring pour forth from the same opening both fresh and salt water? Can a fig tree, my brothers, bear olives, or a grapevine produce figs? Neither can a salt pond yield fresh water” (emphasis mine).
James makes it clear that the lives of Christians should not be characterized by evil speech. By making the analogy of both salt water and fresh water coming from the same spring (which is uncharacteristic of springs), he makes the point that it is uncharacteristic for a believer to have both praise and cursing come from his/her mouth. Nor is it characteristic for us to praise God on one hand and curse our brothers on the other. This, too, is uncharacteristic of a true believer.
Similarly, Jesus explained that what comes out of our mouths is that which fills our hearts. Sooner or later, the evil in the heart comes out through the mouth in curses and swearing. But when our hearts are filled with the goodness of God, praise for Him and love for others will pour forth. Our speech will always indicate what is in our hearts. “The good person out of the good treasure of his heart produces good, and the evil person out of his evil treasure produces evil, for out of the abundance of the heart his mouth speaks” (Luke 6:45).
Why is it a sin to swear/curse? Sin is a condition of the heart, the mind, and “the inner man” (Romans 7:22), which is manifested in our thoughts, actions and words. When we swear and curse, we are giving evidence of the polluting sin in our hearts that must be confessed and repented of. Thankfully, our great God is “faithful and just and will forgive us our sins and purify us from all unrighteousness” (1 John 1:9). When this happens, we receive a new nature from God (2 Corinthians 5:17), our hearts are transformed, and even our speech reflects the new nature God has created within us.