In Matthew 12:35, Jesus says, "A good man out of the good treasure of his heart brings forth good words; an evil man, out of the evil treasure in his heart brings forth evil words." You will notice Jesus uses the word "good" three times, and He uses the word "evil" three times. If the heart is good, then out of the mouth will come words that are good. But if the heart is evil, then out of the mouth will come words that are evil.
In Matthew 7:17-18, Jesus expresses in similar language:
“...every good tree bears good fruit; but the rotten tree bears bad fruit. A good tree cannot produce bad fruit, nor can a rotten tree produce good fruit.” (NAS)
The nature of the tree inevitably determines the kind of fruit. Conversely, when we see the kind of fruit, we know the nature of the tree. The tree is the heart and the fruit is the mouth. If the heart is good, the words that come from the mouth will be good. But if the words that come from the mouth are evil, we know that the heart is evil. You cannot have bad fruit from a good tree, nor can you have good fruit from a bad tree. There is an absolute, inescapable connection between the state of the heart and the state of the mouth.
We may deceive ourselves about the state of our hearts with all sorts of ideas about our own goodness, purity or righteousness, but the sure and unfailing indicator is what comes out of our mouths. If that which comes out of our mouths is corrupt, then the state of our hearts is corrupt. There can be no other conclusion.
I did educational work for five years in East Africa. One of the tribes I worked with was the Marigoli tribe. I was amazed to discover that the same word in that language meant 'heart' and 'voice'. I used to wonder how to determine which one the person meant. Does he mean 'your heart' or 'your voice'? But as I pondered it, I began to see the real insight in the use of that particular language. In reality, the voice indicates the heart. The voice tells with words what the condition of the heart is. It is the same as Jesus said: you cannot have bad words out of a good heart, and you cannot have good words out of a bad heart.
Dear Lord, please help me by Your Holy Spirit to speak good words out of a good heart. Please also help me to think before I speak, to lift my eyes and heart to You and to discern and listen to Your voice. In Jesus’ Name, Amen.