The Fountainhead of Filth Text: Matthew 15:15-20
Introduction: The Religion of Cain
There are, at bottom, only two religions in the world. They have worn different masks and costumes throughout history, but their essential nature remains unchanged. The first is the religion of Cain, the religion of the Pharisees, the religion of secular humanism. It is the religion of externalism. This religion believes that man is fundamentally good, or at least fixable, and that his problems are located outside of him. The problem is his environment, his lack of education, his economic status, or, in the case of the Pharisees, his failure to observe the correct ceremonial procedures. If we can just wash our hands enough, pass enough laws, fund enough programs, and tweak the system just right, we can achieve a state of righteousness.
The second religion is the religion of Abel, the religion of the prophets, the religion of Jesus Christ. This is the religion of the heart. This religion diagnoses the problem with laser precision, and the diagnosis is terminal. The problem is not outside of man; the problem is man. The fountainhead of all the world's misery, corruption, and evil is not in our systems but in our souls. The human heart, in its natural, fallen state, is a geyser of filth. And you cannot fix a poisoned spring by painting the pump handle.
In our text today, Jesus confronts the religion of externalism head-on. The Pharisees, those meticulous guardians of tradition, were appalled that Jesus' disciples ate with unwashed hands. They were concerned with ceremonial defilement, with ritual purity. Jesus uses their superficial objection as a scalpel to lay bare the cancerous heart of the human condition. This is not a quaint historical dispute over Jewish hand-washing techniques. This is the eternal collision between man-made religion and divine revelation. This is God confronting us with the raw, terrifying truth of who we are apart from His grace, and pointing us to the only cure that can possibly work.
The Text
Now Peter answered and said to Him, "Explain the parable to us."
And Jesus said, "Are you still lacking in understanding also?
Do you not understand that everything that goes into the mouth passes into the stomach, and goes into the sewer?
But the things that proceed out of the mouth come from the heart, and those defile the man.
For out of the heart come evil thoughts, murders, adulteries, sexual immoralities, thefts, false witness, slanders.
These are the things which defile the man; but to eat with unwashed hands does not defile the man."
(Matthew 15:15-20 LSB)
Earnest Confusion (v. 15-16)
We begin with Peter, who, as is often the case, serves as the spokesman for the disciples' bewilderment.
"Now Peter answered and said to Him, 'Explain the parable to us.' And Jesus said, 'Are you still lacking in understanding also?'" (Matthew 15:15-16)
Peter's request is honest. He doesn't get it. The preceding statements of Jesus were parabolic, and Peter wants a straight explanation. But Jesus' response is a gentle but firm rebuke. "Are you still lacking in understanding?" The emphasis is on the "still." After all this time walking with Me, hearing My teaching, seeing My works, are you still thinking like the Pharisees? It shows us just how deeply ingrained the religion of externalism is. It is our default setting. Even the chosen apostles, living in the physical presence of the Son of God, struggled to grasp this fundamental truth. This should be a sober warning to all of us. We can be surrounded by sound doctrine and still have a Pharisaical heart, still believing that our spiritual condition is a matter of external management rather than internal transformation.
A Lesson in Spiritual Digestion (v. 17)
Jesus then gives them a lesson in basic biology to make a profound theological point.
"Do you not understand that everything that goes into the mouth passes into the stomach, and goes into the sewer?" (Matthew 15:17 LSB)
Jesus is not being crude for the sake of shock value. He is being devastatingly clear. He is taking the entire complex system of kosher laws and ceremonial washings, which the Pharisees had elevated to the pinnacle of righteousness, and He is showing them its ultimate physical end. Food is fuel for the body. It follows a natural, physical path. It does not and cannot touch the soul, the heart, the conscience. To be defiled means to be rendered unfit for the presence of God. A speck of dirt on your food, or even non-kosher food itself, has no power to do this.
With this one statement, Jesus is effectively declaring the end of the ceremonial food laws. As Mark notes in his parallel account, "Thus he declared all foods clean" (Mark 7:19). Those laws were given to Israel as a teaching tool, to mark them out as a distinct people and to teach them about the difference between the holy and the common. But the Pharisees had turned the teaching tool into the final exam. They had mistaken the shadow for the substance. Jesus, the substance, has now arrived, and He is sweeping the shadows away. The kingdom of God is not a matter of eating and drinking, but of righteousness and peace and joy in the Holy Spirit (Romans 14:17).
The True Source of Pollution (v. 18)
Having dismissed the external, Jesus now identifies the true source of defilement.
"But the things that proceed out of the mouth come from the heart, and those defile the man." (Genesis 15:18 LSB)
This is the central axis of the entire passage. The problem is not what goes in, but what comes out. And what comes out is merely the overflow of what is already inside. The mouth is a bucket brigade for the heart. Your words, your curses, your lies, your slander, your gossip, your flattery, your bitter complaints, these are not unfortunate slips of the tongue. They are accurate readouts of your spiritual state. They are core samples drilled from the center of your being. As Jesus said elsewhere, "out of the abundance of the heart the mouth speaks" (Matthew 12:34). If you want to know what is truly in a man's heart, don't look at his hands; listen to his mouth.
And these things, the things that come from the heart, are what "defile the man." They are what make him common, unclean, and unfit for fellowship with a holy God. Sin is not an external contagion we might catch. It is a terminal, genetic disease we are all born with. We are not sinners because we sin; we sin because we are sinners. The actions are just the symptoms; the disease is in the heart.
A Catalogue of Heart-Sickness (v. 19-20)
Jesus then provides a representative, though not exhaustive, list of the symptoms that flow from this diseased heart.
"For out of the heart come evil thoughts, murders, adulteries, sexual immoralities, thefts, false witness, slanders. These are the things which defile the man; but to eat with unwashed hands does not defile the man." (Matthew 15:19-20 LSB)
Notice that the list begins with "evil thoughts." This is the root. All the other sins on this list are simply evil thoughts that have grown up and gone to work. Murder is the fruit of a heart that first harbored hatred and anger. Adultery is the fruit of a heart that first entertained lust. Theft is the fruit of a heart that first coveted. The list is a direct indictment of humanity's violation of God's moral law, touching on the second table of the Ten Commandments. It is a portrait of the natural man.
This is a radical diagnosis that stands in stark opposition to every form of humanism. The world tells you to "follow your heart." Jesus tells you that your heart is a viper's nest of murder and adultery. The world tells you that you are basically good. Jesus tells you that you are a fountain of filth. The world tells you the problem is "out there." Jesus tells you the problem is in you. Until a man is crushed by the weight of this diagnosis, he will never flee to the only physician who can cure him.
Jesus concludes by bringing the argument full circle. "These are the things which defile the man." The real issue is the corruption of the heart. "But to eat with unwashed hands does not defile the man." The ceremonial stuff is a distraction. The Pharisees were meticulously cleaning the outside of the cup while the inside was full of greed and self-indulgence. They were whitewashing tombs that were full of dead men's bones. And we do the same thing whenever we focus on our external performance, our religious resume, while ignoring the cesspool of pride, envy, and lust that remains in our hearts.
The Great Heart Transplant
If the diagnosis is this grim, what is the cure? If the problem is the heart, then no amount of behavior modification will suffice. You can't teach a crab apple tree to produce Golden Delicious apples by trimming its branches or giving it a pep talk. You need a new tree. And this is precisely what the gospel offers. It does not offer a program for heart-improvement, but a promise of heart-replacement.
God, through the prophet Ezekiel, promised this very thing: "And I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh" (Ezekiel 36:26). This is the new birth. This is regeneration. It is a sovereign, supernatural work of God whereby He rips out our corrupt, sin-producing heart of stone and replaces it with a new, living heart of flesh that desires Him and loves His law.
This great heart transplant was made possible by the work of Jesus Christ. On the cross, He who was perfectly pure in heart took all the filth that proceeds from our hearts upon Himself. He was defiled for us, so that we might be made clean in Him. He took the "murders, adulteries, sexual immoralities, thefts, false witness, slanders" into His own body on the tree. His blood is the only detergent in the universe powerful enough to wash a human heart clean.
Therefore, the Christian life is not one of frantic, Pharisaical hand-washing. It is one of joyful, grateful repentance. We come to God, acknowledging the truth of His diagnosis. We confess that our hearts are indeed fountains of filth. And we plead the blood of Christ, trusting that He has not only forgiven our sins but has also given us a new nature. Our task now is not to suppress the old heart, but to live out of the new one, cultivating the fruit of the Spirit that grows from that new, clean soil. Stop trying to manage your defilement. Come to Christ and be made new.