Words and thoughts carry with them immense power in the continual process of forming your mind. When something is said or even just stated internally, your heart has no choice but to accept it as truth. It accepts intake unilaterally, eating what it is fed, and processes it. It is a completely open gate? It is for this reason that we are told “Above all else, guard your heart, for everything you do flows from it.”
Matthew 5:22 (ESV) states:
“But I say to you that everyone who is angry with his brother will be liable to judgment; whoever insults his brother will be liable to the council; and whoever says, ‘You fool!’ will be liable to the hell of fire.”
What “You’re acting like an idiot” communicates is worlds apart from “You’re an idiot”. The former is stating that the person’s behavior is something that the proverbial idiot would do. The latter, however, is making a judgement call on the person, themselves: In effect, it’s saying that the characteristic of “idiot” is an immutable characteristic of that individual—a core aspect of their being.
While saying this to someone may not seem like a big deal, each time it is said reinforces in your mind that this is truth about that individual, and additionally serves to associate this characteristic of “idiot” with anyone else who makes a similar type of error.
Jesus is talking about these things in the context of murder. Murder is the malicious, intentional ending of life. Physical murder is this type of termination of a physical life. Our emotions and spirit work a bit differently, but the concept is the same, and an analog can be understood as people say the phrase “A little piece of me died when I heard that.”
So then, when we say “You idiot”, in our heart there has occurred the murder of that bit of life. And though we might not recognize the impact it has on our heart, the effect is not diminished any more than eating fish that we don’t know has mercury in it—the toxin is still ingested. The buildup may be gradual and therefore hard to notice, but the cumulative effect is there and the negative impact on various aspects of our life will continue to increase.
The beginning stage of adopting any discipline is difficult, such as the practice of looking at food labels and determining the source of foods you eat. It can feel burdensome and irritating at first, but as you continue it becomes a decreasingly conscious endeavor. Likewise, the practice of more carefully determining the source of our thoughts and words, of “taking every thought captive”, will take time to develop but will ultimately result in healthier thought processes and more life.
One benefit of this practice I can personally attest to is that a lot less work needs to be put into willfully tolerating other people, and you won’t need to spend nearly as much conscious effort in censoring yourself because the source of your words will be in a different state, for “out of the abundance of the heart his mouth speaks.”. As the stacks of death are gradually removed, you just start to think about people differently, and a lot of stress gets released.