1 Peter 3:15

but reverence Christ as Lord in your own hearts. Always be ready with a reply for anyone who calls you to account for the hope you cherish, but answer gently and with a sense of reverence;

Matthew 12:34

You brood of vipers, how can you speak good when you are evil? For the mouth utters what the heart is full of.

Titus 1:10-11

For there are plenty of insubordinate creatures who impose on people with their empty arguments, particularly those who have come over from Judaism;

James 3:6-8

And the tongue is a fire, the tongue proves a very world of mischief among our members, staining the whole of the body and setting fire to the round circle of existence with a flame fed by hell.

2 Peter 2:18

By talking arrogant futilities they beguile with the sensual lure of fleshly passion those who are just escaping from the company of misconduct ??19 promising them freedom, when they are themselves enslaved to corruption (for a man is the slave of whatever overpowers him).

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
but reverence Christ as Lord in your own hearts. Always be ready with a reply for anyone who calls you to account for the hope you cherish, but answer gently and with a sense of reverence;

General references

Matthew 15:18
while what comes out of the mouth comes from the heart ??and that is what defiles a man.