Matthew Henry Commentary Matthew 12:33-37

"Either make the tree good, and its fruit good; or make the tree corrupt, and its fruit corrupt: for the tree is known by its fruit. Ye offspring of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh. The good man out of his good treasure bringeth forth good things: and the evil man out of his evil treasure bringeth forth evil things. And I say unto you, that every idle word that men shall speak, they shall give account thereof in the day of judgment. For by thy words thou shalt be justified, and by thy words thou shalt be condemned." — Matthew 12:33-37 (ASV)

A person's language reveals what country they are from and, likewise, what manner of spirit they possess. The heart is the fountain; words are the streams. A troubled fountain and a corrupt spring must send out muddy and unpleasant streams. Nothing but the salt of grace, cast into the spring, will heal the waters, season the speech, and purify corrupt communication.

An evil person has an evil treasure in their heart, and from it brings forth evil things. Lusts and corruptions, dwelling and reigning in the heart, are an evil treasure, from which the sinner brings forth bad words and actions, to dishonor God and hurt others. Let us keep constant watch over ourselves, that we may speak words agreeable to the Christian character.