"If anyone considers himself religious and yet does not keep a tight rein on his tongue, he deceives himself and his religion is worthless." James 1:26
"Likewise the tongue is a small part of the body, but it makes great boasts. Consider what a great forest is set on fire by a small spark. 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. All kinds of animals, birds, reptiles and creatures of the sea are being tamed and have been tamed by man, but no man can tame the tongue. It is a restless evil, full of deadly poison. With the tongue we praise our Lord and Father, and with it we curse men, who have been made in God’s likeness. Out of the same mouth come praise and cursing. My brothers, this should not be." James 3:5-10
"The tongue has the power of life and death, and those who love it will eat its fruit." Proverbs 18:21
Everything we say either brings life, or it brings death. Now, there's more I could add to this (a lot more), but I think I'll just let the above verses be our instruction.