1 Peter 3:15

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

Matthew 12:34

Ye brood of vipers, how can ye, being evil, speak good things? For out of the abundance of the heart the mouth speaketh.

Titus 1:10-11

For there are many unruly vain-talkers and deceivers, especially they of the circumcision,

James 3:6-8

And the tongue is a fire, a world of iniquity: it is the tongue among the members which defileth the whole body and setteth on fire the course of nature, and is set on fire of hell.

2 Peter 2:18

For by speaking swelling words of vanity, they allure thro' the desire of the flesh, thro' wantonness, those that were clean escaped from them that 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.

Heart

General references

Bible References

Heart

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

General references

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