If anyone considers himself religious and yet does not keep a tight rein on his tongue, he deceives himself and his religion is worthless.
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.
But I tell you that men will have to give account on the day of judgment for every careless word they have spoken. For by your words you will be acquitted, and by your words you will be condemned
1 Timothy 4:12
Don't let anyone look down on you because you are young, but set an example for the believers in speech, in life, in love, in faith and in purity.
The tongue also is a fire, a world of evil among the parts of the body. It corrupts the whole person, sets the whole course of his life on fire, and is itself set on fire by hell.
But now you must rid yourselves of all such things as these: anger, rage, malice, slander, and filthy language from your lips.