Proverbs 15:28

A heart of righteousness will ponder the answer, but a mouth of wickedness will pour out deceit.

1 Peter 3:15

but set Christ apart [as] Lord in your hearts, always ready to [make] a defense to anyone who asks you [for] an accounting concerning the hope [that is] in you.

Proverbs 15:2

The tongue of the wise will dispense knowledge, but the mouth of fools will pour out folly.

1 Kings 3:23-28

Then the king said, "This one [is] saying, 'This [is] my son, the living one, but your son [is] the dead one,' and the other one keeps saying, 'But no! Your son [is] the dead one, and my son [is] living!'"

Proverbs 10:19

In many words, transgression is not lacking, but he who restrains his lips is prudent.

Proverbs 13:16

Anyone who is clever will act with intelligence, but the fool will display folly.

Proverbs 16:23

The heart of the wise will make his mouth judicious, and upon his lips, it will add persuasiveness.

Proverbs 29:11

A fool gives all his breath, but [the] wise holds back in quiet.

Proverbs 29:20

You see a man who is hasty in his words: [there is more] hope for a fool than him.

Ecclesiastes 5:2

Do not be rash with your mouth, and do not let your heart be quick to utter a word before God. For God is in heaven, and you [are] on earth; therefore, let your words be few.

Ecclesiastes 5:6

Do not let your mouth lead your flesh into sin, and do not tell the messenger that it [was] a mistake. Why anger God at your words, so that he destroys the work of your hands?

Ecclesiastes 10:12-14

The wise man [wins] favor by the words of his mouth, but the fool is devoured by his own lips.

Matthew 12:34

Offspring of vipers! How are you able to say good things [when you] are evil? For from the abundance of the heart the mouth speaks.

Titus 1:10-11

For there are many rebellious [people], idle talkers and deceivers, especially those of the circumcision,

James 3:6-8

And the tongue [is] a fire! The world of unrighteousness, the tongue, is set among our members, defiling the whole body and setting on fire {the course of human existence}, being set on fire by hell.

2 Peter 2:18

{For by speaking high-sounding but empty words}, they entice with desires of the flesh [and] with licentiousness those who are scarcely escaping from those who live in error,

Treasury of Scripture Knowledge

Summary

The heart of the righteous studieth to answer: but the mouth of the wicked poureth out evil things.

General references

Bible References

Heart

Proverbs 15:2
The tongue of the wise will dispense knowledge, but the mouth of fools will pour out folly.
Proverbs 16:23
The heart of the wise will make his mouth judicious, and upon his lips, it will add persuasiveness.
1 Kings 3:23
Then the king said, "This one [is] saying, 'This [is] my son, the living one, but your son [is] the dead one,' and the other one keeps saying, 'But no! Your son [is] the dead one, and my son [is] living!'"
Ecclesiastes 5:2
Do not be rash with your mouth, and do not let your heart be quick to utter a word before God. For God is in heaven, and you [are] on earth; therefore, let your words be few.
1 Peter 3:15
but set Christ apart [as] Lord in your hearts, always ready to [make] a defense to anyone who asks you [for] an accounting concerning the hope [that is] in you.

General references

Proverbs 14:33
In the heart of him who has understanding, wisdom rests, but [even] in the midst of fools it becomes known.
Matthew 15:18
But the things that come out of the mouth come from the heart, and these defile the person.