The words you utter can defile you (i.e., keep you out of the presence of God).
People who take holiness seriously must take sin seriously. This means that we must have clear definitions of what sin is and what sin isn’t. If sin keeps us from the redeeming presence of God, then we have to be sure that we’re doing all we can, by grace and with the help of the Holy Spirit, to refrain from sinning.
Isn’t it interesting, then, that Jesus says, “it is not what goes into the mouth that defiles a person, but what comes out of the mouth“ (Matt 15:11). This means that what we say can keep us from God’s presence.
Normally we think of sins in terms of sins of commission (doing what we shouldn’t do), or sins of omission (failing to do what God instructs us to do). Our attitudes, thoughts, and emotions can also be sinful.
However, Jesus takes this one step further by saying that the words we speak can defile us. The question is, how?
Jesus answers this question when he says to the Pharisees,
You brood of vipers! How can you speak good, when you are evil? For out of the abundance of the heart the mouth speaks. The good person out of his good treasure brings forth good, and the evil person out of his evil treasure brings forth evil. I tell you, on the day of judgment people will give account for every careless word they speak, for by your words you will be justified, and by your words you will be condemned.Matt 12:34–37
In other words, words express our inner thoughts; the shape and contour of our hearts; the content of our character; the status of our spiritual health. Harmful and ugly speech is evidence of a lack of true internal cleansing.
To this same point, Jesus says, “For out of the overflow of the heart the mouth speaks” (Matt 12:34).
God is willing and able to do an inner work in our lives. He wants to shape our hearts. The aim is internal cleansing. He can purify our thoughts. This is the promise of the resurrection that comes with the filling of the Holy Spirit. When we’re internally clean our words honor him. This is why Paul says, “Let there be no filthiness nor foolish talk nor crude joking, which are out of place, but instead let there be thanksgiving” (Eph 5:4).
Do you want to know what’s in your heart? Do you want to know the status of your spiritual health and being in Jesus? Pay attention to what you say (or what you think and feel). For Jesus, harmful harmful thoughts toward others is an expression of character and is contaminating.
I finish with a quote from John Wesley’s Plain Account of Christian Perfection:
For he saith not, The blood of Christ will cleanse, (at the hour of death, or in the day of judgment,) but it `cleanseth,’ at the time present, us living Christians `from all sin.’ And it is equally evident, that if any sin remain, we are not cleansed from `all’ sin. If any unrighteousness remain in the soul, it is not cleansed from `all, unrighteousness. Neither let any say that this relates to justification only, or the cleansing us from the guilt of sin: First, because this is confounding together what the Apostle clearly distinguishes, who mentions, first, `to forgive us our sins, and then `to cleanse us from all unrighteousness.’ Secondly, because this is asserting justification by works, in the strongest sense possible; it is making all inward, as well as all outward, holiness, necessarily previous to justification. For if the cleansing here spoken of is no other than the cleansing us from the guilt of sin, then we are not cleansed from guilt, that is, not justified, unless on condition of walking `in the light, as he is in the light.’ It remains, then, that Christians are saved in this world from all sin, from all unrighteousness; that they are now in such a sense perfect, as not to commit sin, and to be freed from evil thoughts and evil tempers.”John Wesley. “A Plain Account of Christian Perfection”