18 And he saith unto them, Are ye so without understanding also? Perceive ye not, that whatsoever from without goeth into the man, [it] cannot defile him; 19 because it goeth not into his heart, but into his belly, and goeth out into the draught? [This he said], making all meats clean.
Matthew Henry's Commentary on Mark 7:18-19
Commentary on Mark 7:14-23
(Read Mark 7:14-23)
Our wicked thoughts and affections, words and actions, defile us, and these only. As a corrupt fountain sends forth corrupt streams, so does a corrupt heart send forth corrupt reasonings, corrupt appetites and passions, and all the wicked words and actions that come from them. A spiritual understanding of the law of God, and a sense of the evil of sin, will cause a man to seek for the grace of the Holy Spirit, to keep down the evil thoughts and affections that work within.