1 Peter 3:15

and be always ready to answer every one that asketh you a reason of the hope that is in you, with meekness and reverence:

Matthew 12:34

O race of vipers, how can ye speak good things, who are yourselves so wicked? for out of the abundance of the heart the mouth speaketh.

Titus 1:10-11

For there are many disorderly persons, vain-talkers and deceivers, especially those of the circumcision; whose mouths must be stopped:

James 3:6-8

And the tongue is a fire, a world of iniquity: so is the tongue among our several parts, defiling the whole body, inflaming the course of nature, and is set on fire by hell.

2 Peter 2:18

For when they speak swelling words of vanity, they ensnare in the lusts of the flesh, through their lasciviousness, those who had indeed withdrawn from such as deal in error;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.

Heart

General references

Bible References

Heart

1 Peter 3:15
and be always ready to answer every one that asketh you a reason of the hope that is in you, with meekness and reverence:

General references

Matthew 15:18
But the things, which proceed out of the mouth, come from the heart, and those defile a man.