James 1:26
If anyone considers himself religious and yet does not bridle his tongue, he deceives his heart and his religion is worthless.

Matthew 12:34-37
You brood of vipers, how can you who are evil say anything good? For out of the overflow of the heart the mouth speaks. / The good man brings good things out of his good store of treasure, and the evil man brings evil things out of his evil store of treasure. / But I tell you that men will give an account on the day of judgment for every careless word they have spoken. ...

Ephesians 4:25
Therefore each of you must put off falsehood and speak truthfully to his neighbor, for we are all members of one another.

Colossians 3:8-9
But now you must put aside all such things as these: anger, rage, malice, slander, and filthy language from your lips. / Do not lie to one another, since you have taken off the old self with its practices,

Psalm 34:13
Keep your tongue from evil and your lips from deceitful speech.

1 Peter 3:10
For, “Whoever would love life and see good days must keep his tongue from evil and his lips from deceitful speech.

James 3:5-10
In the same way, the tongue is a small part of the body, but it boasts of great things. Consider how small a spark sets a great forest ablaze. / The tongue also is a fire, a world of wickedness among the parts of the body. It pollutes the whole person, sets the 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, ...

Matthew 15:18-19
But the things that come out of the mouth come from the heart, and these things defile a man. / For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false testimony, and slander.

Psalm 15:1-3
A Psalm of David. O LORD, who may abide in Your tent? Who may dwell on Your holy mountain? / He who walks with integrity and practices righteousness, who speaks the truth from his heart, / who has no slander on his tongue, who does no harm to his neighbor, who casts no scorn on his friend,

1 John 3:15
Everyone who hates his brother is a murderer, and you know that eternal life does not reside in a murderer.

Leviticus 19:16
You must not go about spreading slander among your people. You must not endanger the life of your neighbor. I am the LORD.

Romans 1:29-30
They have become filled with every kind of wickedness, evil, greed, and depravity. They are full of envy, murder, strife, deceit, and malice. They are gossips, / slanderers, God-haters, insolent, arrogant, and boastful. They invent new forms of evil; they disobey their parents.

Psalm 101:5
Whoever slanders his neighbor in secret, I will put to silence; the one with haughty eyes and a proud heart, I will not endure.

1 Timothy 5:13
At the same time they will also learn to be idle, going from house to house and being not only idle, but also gossips and busybodies, discussing things they should not mention.

Titus 3:2
to malign no one, and to be peaceable and gentle, showing full consideration to everyone.