Matthew 12:34-35

You brood of snakes! how can you, bad as you are, utter anything good? For the mouth says only what the heart is full of.

Colossians 3:16

Let the message of Christ live in your hearts in all its wealth of wisdom. Teach it to one another and train one another in it with thankfulness, with psalms, hymns, and sacred songs, and sing to God with all your hearts.

Treasury of Scripture Knowledge

Summary

The heart of the wise teacheth his mouth, and addeth learning to his lips.

Bible References

Heart

Matthew 12:34
You brood of snakes! how can you, bad as you are, utter anything good? For the mouth says only what the heart is full of.
Colossians 3:16
Let the message of Christ live in your hearts in all its wealth of wisdom. Teach it to one another and train one another in it with thankfulness, with psalms, hymns, and sacred songs, and sing to God with all your hearts.