From an October 1987 general conference address.
Take Not the Name of God in Vain24971_000_006
President Hinckley reminds us to speak only uplifting words so that we can honor God and be an example to others.
There is an evil and growing habit of the use of filthy language. The taking of the Lord’s name in vain is a most serious matter.
When I was in the first grade, I experienced what I thought was a rather tough day at school. I came home, walked in the house, threw my book on the kitchen table, and let forth [some bad words] that included the name of the Lord.
My mother was shocked. She told me quietly, but firmly, how wrong I was. She told me that I could not have words of that kind coming out of my mouth. She led me by the hand into the bathroom, where she took from the shelf a clean washcloth, put it under the faucet, and then generously coated it with soap. She said, “We’ll have to wash out your mouth.” She told me to open it, and I did so reluctantly. Then she rubbed the soapy washcloth around my tongue and teeth. I sputtered and fumed and felt like swearing again, but I didn’t. I rinsed and rinsed my mouth, but it was a long while before the soapy taste was gone. In fact, whenever I think of that experience, I can still taste the soap. I have tried to avoid using the name of the Lord in vain since that day. I am grateful for that lesson.
If you have the habit, how do you break it? You begin by making a decision to change. The next time you are prone to use words you know to be wrong, simply stop. Keep quiet or say what you have to say in a different way. As you practice such restraint, it will become easy.
Remember that it is the same voice which prays to the Lord on the one hand which, on the other hand, may be [tempted] to speak language foul and filthy.
Don’t swear. Don’t profane. Avoid so-called dirty jokes. Stay away from conversation that is sprinkled with foul and filthy words. You will be happier if you do so, and your example will give strength to others.