After calling the Pharisees hypocrites because they declare certain people unclean based on ritual purity or food traditions, Jesus describes what really defiles a person (Matthew 15:10-20). It is not external things life food that make a person unclean, but what comes out of their heart.
The verb translated “defile” (κοινόω) refers to making something or someone ritually unclean. For example, it is used to described Peter’s attitude toward the Gentile Cornelius (Acts 10:15; 11:9). Paul is accused of bringing an unclean Gentile into the Temple courts, “defiling this holy place” (Acts 21:28). The irony is the Pharisees tried to remain in a state of purity, yet by focusing on external purity the Pharisees do not understand what defiles a person.
Following John Nolland, both Jesus and the Pharisees are concerned with the purity of God’s people, but they were pushing in different directions (Matthew, 621). For the Pharisee, defilement could be avoided by closer attention to what renders a person ritually unclean, things in the external world that might be touched. For Jesus, he sees defilement as the things coming out of a person, their moral and ethical choices. Jesus is not challenging Torah purity laws (he is not advocating eating unclean foods), but by allowing his disciples to not practice hand washing according to the traditions of the elders, he is rejecting some of the practices of the Pharisees.
The disciples tell Jesus has offended the Pharisees (15:12-14). Some of the disciples approach Jesus and tell him the Pharisees were offended by this harsh condemnation, especially since Jesus publicly called them hypocrites. In Mark 7:17, this conversation takes place in private, back in the house, Matthew does not follow Mark here so that this speech happens in front of the crowd as well.
Jesus does not seem to care if he has offended the Pharisees (after all, they publicly called him an agent of Satan!) He predicts they will be “uprooted” when the kingdom comes and telling his disciples to “leave them, they are blind guides.” John the Baptist said a similar thing in Matthew 3:10, the axe is already at the root and every tree that is not bearing fruit will be cut down and thrown into the fire.
Jesus says evil thoughts come out of the heart (15:15-20). When Peter asks Jesus to explain the parable, Jesus says he is still “without understanding” (15:15-16). Mark 7:17 does not identify the speaker, Matthew has already included Peter’s attempt to walk on the water, so he is building up to Peter’s confession in 16:16.
The word translated “without understanding” in the ESV (ἀσύνετος) has the connotation of senseless, foolish, or as the NIV translates, “a dullard.” BrillDAG suggests “obtuse, stupid.” The word is sometimes translated “foolish” and is rare in the New Testament. Paul uses it the other three times it is used, twice in Romans 1 to describe the foolishness of mankind in rejecting the creator, and once in chapter 10 of Romans to describe the foolishness of the nation of Israel in rejecting God.
Perhaps Jesus is not saying “Are you a dullard?” but more like “haven’t you started getting with it spiritually yet?” The disciples do not understand a simple parable in context, something they ought to have understood by this point in the story. In 15:10 Jesus told his listeners to “hear and understand,” one would expect this closest disciple to understand. At this point Peter does not understand what defiles a person.
What goes into a body does not matter as much as what comes out (15:17-20). Food simply passes through the body, but “evil thoughts” start inside the body and come out in the form of offenses against God’s character. For reasons that are not clear to me, the ESV and NIV do not translate the Greek phrase εἰς ἀφεδρῶνα, into the latrine. The NRSV properly translates the phrase “and goes out into the sewer.”
The rest of the list is more or less the Ten Commandments (Murder, adultery, sexual immorality, theft, false witness, slander). Jesus discussed murder and adultery in the Sermon on the Mount (Matt 5:21-32). Matthew re-arranges and reduces Mark’s list, omitting acts of avarice, deceit, licentiousness, and evil eye, pride and folly. “Jesus sticks with matters which in Jewish terms would not only be immoral but also criminal…all his items relate to the Ten Commandments” (Nolland, Matthew, 627). Jesus referred to the fifth commandment in the previous paragraph, the fourth commandment in 12:1-14. True worship is the theme of the first three commandments, so potentially 15:7-9 covers the rest of the commandments.
In verse 20 Jesus states eating with unwashed hands does not defile anyone. This is different than Mark 7:19, the parenthetical comment (by this Jesus declared all foods clean). Virtually every translation takes these as words of Jesus, but it is possible these are Matthew’s conclusion to the matter, clarifying Mark’s interpretation of Jesus’s words.
Jesus makes a clear contrast between what defiles a person according to the Pharisees and what actually causes defilement. Jesus does not declare all foods clean here, nor does he allow his disciples to break the Law.