It is not what you say or what you do that are the most important thing in your life, but who you are. It is from who you are that everything else flows. This is why trying to change our behaviour is an exercise in futility. We may be able to change for a short period of time but eventually we will slide back to the nature of our heart. It is not unlike healthy living.
There is a difference between healthy living and dieting. Dieting is a short term solution for a long term problem. It doesn't deal with the underlying problem of an unhealthy lifestyle. It deals with a symptom instead of the disease. Healthy living goes to the heart and changes perspective and attitude. It is a complete change of lifestyle with a change of eating being part of it. It cannot be applied from an outside pressure but must be a personal conviction that everything has to change. It is a good metaphor of the Christian experience.
Christianity is not about "dieting"; a short term solution for a long term problem. It is not about conforming our behaviour or our vocabulary under the pressure of an outside force. That is just an act of self-improvement and soon enough a person will slip back to their natural selves. Our problem is our nature, the condition of our heart. There needs to be a change of perspective, a change of attitude, a change of heart and that only happens with the transforming power of Jesus Christ.
We cannot hide our true colours, our true nature for long, and it soon becomes evident to everyone, although not everyone will admit it. We tend to like people even when we know that things aren't quite right. We consider if they are going to church everything is okay but we have a lot of "conforming" people in our pews who need to be told that they need the transformation of Jesus. The reason their condition is obvious was taught by Jesus:
For a good tree does not bear bad fruit, nor does a bad tree bear good fruit. (Luke 6:43)
A healthy tree is going to give you healthy fruit. A diseased and dried up tree is going to give you diseased and dried up fruit. The life filled and led by the Holy Spirit is going to bear the fruit of the Spirit. The life filled and controlled by sin is going to bear the fruit of sin. Not everyone attending church is bearing the fruit of the Spirit and there is a reason for it. There is no getting around it. One is a transformed life, the others is attempting conformity.
For every tree is known by its own fruit. For men do not gather figs from thorns, nor do they gather grapes from a bramble bush. (v. 44)
We are known by our fruit. It is not the fruit that defines us but we who define the fruit that is produced. An apple tree produces apples, not an apple that makes it an apple tree. Behaviour and words do not make us a sinner, it is being a sinner that produces behaviour and words. An apple tree cannot produce oranges just because it wants to; there would have to be a transformation of its nature. A sinner cannot be righteous just because he wills it. We need the transformation that Jesus offers.
A good man out of the good treasure of his heart brings forth good; and an evil man out of the evil treasure of his heart brings forth evil. (v. 45)
We have sayings such as, "a leopard can't change his spots", but still we fail to understand it. We were born a sinner. By nature we are sinners, in complete rebellion against Yahweh. We see the evidence of such rebellion all around us today but fail to recognize it in ourselves. Knowing that we do bad things we try to improve ourselves, change our behaviour, our vocabulary, our attitude. But we can't for long because our true nature is always going to reveal itself. The only way to become a "good man" is by the blood of Jesus Christ. No other way will do; not conformity, self-will, self-improvement, thinking good thoughts, or acts of kindness. Jesus said he is the only way.
Jesus told us:
For out of the abundance of the heart his mouth speaks. (v. 45)
It isn't about what we say or what we do but instead who we are. Who we are determines what we do and what we say. It is out of the abundance of our heart that we speak. If that abundance is Jesus' righteousness then these words will be righteous. If the abundance is from a non-transformed heart then it will be evil that we speak. It's as simple as that.