Matthew 15:18

But the things that come out of a person's mouth come from his heart. These are what [spiritually] corrupt a person.

Matthew 12:34

You children of snakes! Since you are evil, how do you expect to speak good things? For the mouth speaks what the heart is filled with.

Matthew 15:11

It is not what enters the mouth of a person that [spiritually] corrupts him, but what proceeds out of his mouth that [spiritually] corrupts him."

James 3:6-10

And the tongue is [like] a fire [i.e., like that spark]. [For] the tongue, as a part of the body, is [like] the world of evil. It corrupts the entire life [of a person] and inflames the course of nature itself [i.e., it affects a person throughout his whole earthly existence], and is ignited by hell itself [i.e., the evil produced by the fiery tongue has hell as its source and destiny].

Luke 19:22

The gentleman replied to him, 'I will judge you [based] on what you [yourself] have [just] said, you evil slave. [Since] you knew that I am a hard man to deal with, picking up [and keeping] something I had not laid down, and harvesting a crop I had not planted,

Revelation 13:5-6

And the beast was given [by the dragon ?] a mouth for making proud claims and [speaking] blasphemous words, and the authority to act for forty-two months [See 11:2; 12:6].

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 the mouth of a person that [spiritually] corrupts him, but what proceeds out of his mouth that [spiritually] corrupts him."
Matthew 12:34
You children of snakes! Since you are evil, how do you expect to speak good things? For the mouth speaks what the heart is filled with.
Luke 19:22
The gentleman replied to him, 'I will judge you [based] on what you [yourself] have [just] said, you evil slave. [Since] you knew that I am a hard man to deal with, picking up [and keeping] something I had not laid down, and harvesting a crop I had not planted,
James 3:6
And the tongue is [like] a fire [i.e., like that spark]. [For] the tongue, as a part of the body, is [like] the world of evil. It corrupts the entire life [of a person] and inflames the course of nature itself [i.e., it affects a person throughout his whole earthly existence], and is ignited by hell itself [i.e., the evil produced by the fiery tongue has hell as its source and destiny].
Revelation 13:5
And the beast was given [by the dragon ?] a mouth for making proud claims and [speaking] blasphemous words, and the authority to act for forty-two months [See 11:2; 12:6].