Matthew 15:18

But the things that come out from the mouth proceed from the heart, and it is these that defile a man;

Matthew 12:34

You brood of vipers! how can you, evil as you are, say anything good? For what fills the heart will rise to the lips.

Matthew 15:11

It is not what enters a man's mouth that 'defiles' him, but what comes out from his mouth--that does defile him!"

James 3:6-10

And the tongue is like a spark. Among the members of our body it proves itself a very world of mischief; it contaminates the whole body; it sets the wheels of life on fire, and is itself set on fire by the flames of the Pit.

Luke 19:22

The master answered 'Out of your own mouth I judge you, you worthless servant. You knew that I am a stern man, that I take what I have not planted, and reap what I have not sown?

Revelation 13:5-6

The Beast was given 'a mouth that spoke proudly' and blasphemously, and it was empowered to work its will for forty-two months.

Treasury of Scripture Knowledge

Summary

But those things which proceed out of the mouth come forth from the heart; and they defile the man.

Bible References

General references

Matthew 15:11
It is not what enters a man's mouth that 'defiles' him, but what comes out from his mouth--that does defile him!"
Matthew 12:34
You brood of vipers! how can you, evil as you are, say anything good? For what fills the heart will rise to the lips.
Luke 19:22
The master answered 'Out of your own mouth I judge you, you worthless servant. You knew that I am a stern man, that I take what I have not planted, and reap what I have not sown?
James 3:6
And the tongue is like a spark. Among the members of our body it proves itself a very world of mischief; it contaminates the whole body; it sets the wheels of life on fire, and is itself set on fire by the flames of the Pit.
Revelation 13:5
The Beast was given 'a mouth that spoke proudly' and blasphemously, and it was empowered to work its will for forty-two months.