Out of the overflow of the heart the mouth speaks. Swearing expresses anger and leads to further aggressive behavior, including road rage, verbal fights, and physical violence. Jesus had a lot to say about the power and importance of every word we speak. According to the Lord, the need for change goes far deeper than curbing our tongues.
Clean speech comes from being clean inside.
Too often, we try to scrub the bucket of our mouths instead of purifying the water in the well of our hearts. A friend told me about a man whose daily speech was so profane that when he talked aloud in his sleep, he swore. After he became a Christian, he began memorizing Scripture, a few verses every week. That didn't stop his nocturnal commentary, but it changed what he said. Instead of swearing, he began quoting the Bible in his sleep.