18 But what comes out of the mouth proceeds from the heart, and this is what defiles. 19 For out of the heart come evil intentions, murder, adultery, fornication, theft, false witness, slander. 20 These are what defile a person, but to eat with unwashed hands does not defile."
Matthew Henry's Commentary on Matthew 15:18-20
Commentary on Matthew 15:10-20
(Read Matthew 15:10-20)
Christ shows that the defilement they ought to fear, was not from what entered their mouths as food, but from what came out of their mouths, which showed the wickedness of their hearts. Nothing will last in the soul but the regenerating graces of the Holy Spirit; and nothing should be admitted into the church but what is from above; therefore, whoever is offended by a plain, seasonable declaration of the truth, we should not be troubled at it. The disciples ask to be better taught as to this matter. Where a weak head doubts concerning any word of Christ, an upright heart and a willing mind seek for instruction. It is the heart that is desperately wicked, Jeremiah 17:9, for there is no sin in word or deed, which was not first in the heart. They all come out of the man, and are fruits of that wickedness which is in the heart, and is wrought there. When Christ teaches, he will show men the deceitfulness and wickedness of their own hearts; he will teach them to humble themselves, and to seek to be cleansed in the Fountain opened for sin and uncleanness.