Look at the ships also, though they are so great and are driven by strong winds, are still directed by a very small rudder wherever the inclination of the pilot desires. So also the tongue is a small part of the body, and yet it boasts of great things. See how great a forest is set aflame by such a small fire! And the tongue is a fire, the very world of iniquity; the tongue is set among our members as that which defiles the entire body, and sets on fire the course of our life, and is set on fire by hell. For every species of beasts and birds, of reptiles and creatures of the sea, is tamed and has been tamed by the human race. But no one can tame the tongue; it is a restless evil and full of deadly poison. James 3:4-8
You can destroy your life with what you say. In a moment of foolishness, you can hurt others, ruin your reputation, and dishonor God. An undisciplined tongue is the hallmark of a fool. Discipline in what you say, along with listening and calm control, are markers of a mature Christian . . .
But everyone must be quick to hear, slow to speak and slow to anger; for the anger of man does not achieve the righteousness of God. James 1:19
The things you say also reveal what is in your heart. Listen to what people say and understand what they really are. . .
The good man out of the good treasure of his heart brings forth what is good; and the evil man out of evil treasure brings forth what is evil; for his mouth speaks that which fills his heart Luke 6:45
Here Jesus tells us that the things you say are so impactful that judgment and salvation hang in the balance . . .
But I say unto you, That every idle word that men shall speak, they shall give account thereof in the day of judgment. For by thy words thou shalt be justified, and by thy words thou shalt be condemned. Matthew 12:36-37
Those who live in Christ, seeking the approval of God above all else, say things that are different from those who are lost in the world. People who spew boastful arrogance, slander (tearing others down), obscenities; offensive, malicious, and derogatory gossip are displeasing to God. Not to mention those who dishonor and disparage God, using his name as profanity! This is all filth from the world and should not be present in those who live in Christ. What you say matters and you will be held accountable for what comes out of your mouth.
But I tell you that every careless word that people speak, they shall give an account for it in the day of judgment. For by your words you will be justified, and by your words you will be condemned. Matthew 12:36-37
Often the best plan is to keep your mouth shut. Unless you are sure what you are about to say is rooted in the truth, adds some value, is not self-serving, and is pleasing to God, you are best served to keep it to yourself.
Even a fool, when he keeps silent, is considered wise; when he closes his lips, he is considered prudent. Proverbs 17:28