Here are many Bible verses about speech.

Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear.- Ephesians 4:29

Let the words of my mouth and the meditation of my heart be acceptable in your sight, O Lord, my rock and my redeemer.- Psalm 19:14

My mouth shall speak wisdom; the meditation of my heart shall be understanding.- Psalm 49:3

Know this, my beloved brothers: let every person be quick to hear, slow to speak, slow to anger;- James 1:19

Gracious words are like a honeycomb, sweetness to the soul and health to the body.- Proverbs 16:24

The mouth of the righteous utters wisdom, and his tongue speaks justice. The law of his God is in his heart; his steps do not slip.- Psalm 37:30-31

Rather, speaking the truth in love, we are to grow up in every way into him who is the head, into Christ,- Ephesians 4:15

But as you excel in everything—in faith, in speech, in knowledge, in all earnestness, and in our love for you—see that you excel in this act of grace also.- 2 Corinthians 8:7

The good person out of the good treasure of his heart produces good, and the evil person out of his evil treasure produces evil, for out of the abundance of the heart his mouth speaks.- Luke 6:45

As long as my breath is in me, and the spirit of God is in my nostrils, my lips will not speak falsehood, and my tongue will not utter deceit.- Job 27:3-4

Let your speech always be gracious, seasoned with salt, so that you may know how you ought to answer each person.- Colossians 4:6