1 Peter 3:15
but in your hearts reverence Christ as Lord. Always be prepared to make a defense to everyone who asks you to give an account for the hope that is in you, yet do it with gentleness and respect;
Matthew 12:34
You brood of vipers! how can you speak good, when you are evil? For out of the abundance of the heart the mouth speaks.
Titus 1:10-11
For there are many rebellious men, empty talkers and deceivers, especially those of the circumcision.
James 3:6-8
And the tongue is a fire, a world of evil among the members of the body. The tongue corrupts our whole person, sets the whole course of our life on fire, and is itself set on fire by hell.
2 Peter 2:18
For speaking out arrogant words of vanity, they entice by fleshly desires, by sensuality, those who barely escape from the ones who live in error.