Right use of the tongue

In John Calvin's discussion of Jesus' words to the brood of vipers in Matthew 12:33-37 he excursively discusses the "idle" or "useless word, one which produces no edification or fruit"

... if we consider the use for which our tongues were formed we shall agree that they are justly guilty who devote their tongues recklessly to trifling nonsense and so prostitute them. It is a serious fault to abuse with frivolities the time which Paul bids us anxiously to redeem (Col. 4.5). But since no-one is so sparing in speech and so wise and temperate that he does not sometimes sink into some idle words, nothing would remain for us all but desperation if God acted towards us with strict Law. But since our trust in our salvation is founded on God not entering into judgment with us but freely burying in oblivion our sins which deserve unnumbered deaths, let us not doubt that when He wipes out the guilt of our whole life He therewith pardons the sin of empty speaking. For when Scripture speaks of God's judgment it is not at all overturning the forgiveness of sins. Nobody should be permissive to himself, however, but should be careful to keep a tight reign on his tongue. First so that we may speak reverently and soberly about the holy mysteries of God, and then that we may abstain from buffoonery and empty witticisms, and much more from hostile vituperation, and lastly that we may ensure that our word is seasoned with salt (Col. 4.6).

Proverbs 15: 2 The tongue of the wise uses knowledge rightly, but the mouth of fools pours forth foolishness.

Colossians 4:5-6 Walk in wisdom toward those who are outside, redeeming the time. Let your speech always be with grace, seasoned with salt, that you may know how you ought to answer each one.

1 Peter 3:10 For “ He who would love life and see good days, let him refrain his tongue from evil, and his lips from speaking deceit.

James 1:26 If anyone among you thinks he is religious, and does not bridle his tongue but deceives his own heart, this one’s religion is useless.

James 3:1-12

Psalm 120:2 Deliver my soul, O LORD, from lying lips and from a deceitful tongue.

Proverbs 10:20 The tongue of the righteous is choice silver; the heart of the wicked is worth little.

Proverbs 12:18 There is one who speaks like the piercings of a sword, but the tongue of the wise promotes health.

Zephaniah 3:13 The remnant of Israel shall do no unrighteousness and speak no lies, nor shall a deceitful tongue be found in their mouth; for they shall feed their flocks and lie down, and no one shall make them afraid.”