Matthew 12:34-35

O vipers' brood, how can you speak what is good when you are evil? For it is from the overflow of the heart that the mouth speaks.

Colossians 3:16

Let the teaching concerning Christ remain as a rich treasure in your hearts. In all wisdom teach and admonish one another with psalms, hymns, and spiritual songs, and sing with grace in your hearts to God.

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
O vipers' brood, how can you speak what is good when you are evil? For it is from the overflow of the heart that the mouth speaks.
Colossians 3:16
Let the teaching concerning Christ remain as a rich treasure in your hearts. In all wisdom teach and admonish one another with psalms, hymns, and spiritual songs, and sing with grace in your hearts to God.