Matthew 15:18

But the things that come out of the mouth come from the heart, and they make the man foul.

Matthew 12:34

You brood of vipers! How can you, wicked as you are, say anything that is good? For the mouth talks about the things that fill the heart.

Matthew 15:11

It is not what goes into a man's mouth that makes him foul; no, it is what comes out of a man's mouth that makes him foul."

James 3:6-10

And the tongue is a fire, and takes its place among the parts of our bodies as a world of evil; it soils the whole body and sets on fire the circle of man's nature, and itself is set on fire by hell.

Luke 19:22

He said to him, 'On the ground of what you say I will sentence you, you wicked slave! You knew that I was a stern man, that I picked up what I did not put down, and reaped what I did not sow.

Revelation 13:5-6

Then there was given to the wild beast a mouth that uttered boastful, blasphemous words, and permission to wield his authority 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 goes into a man's mouth that makes him foul; no, it is what comes out of a man's mouth that makes him foul."
Matthew 12:34
You brood of vipers! How can you, wicked as you are, say anything that is good? For the mouth talks about the things that fill the heart.
Luke 19:22
He said to him, 'On the ground of what you say I will sentence you, you wicked slave! You knew that I was a stern man, that I picked up what I did not put down, and reaped what I did not sow.
James 3:6
And the tongue is a fire, and takes its place among the parts of our bodies as a world of evil; it soils the whole body and sets on fire the circle of man's nature, and itself is set on fire by hell.
Revelation 13:5
Then there was given to the wild beast a mouth that uttered boastful, blasphemous words, and permission to wield his authority for forty-two months.