Verses 18, 19. - Our Lord had already, in his sermon on the mount, taught his disciples fully wherein purity or impurity of heart consists, and he might, therefore, with good reason, ask them how it was that they, even they who had been so favored by being constantly with him, had forgotten or misunderstood him. Our Lord's illustration is physically accurate. The portion carried off is that which by its removal purifies what remains. The part which is available for nourishment is, in its passage through the system, converted into chyle, the matter from which the blood is formed. What is not available for nourishment passes away into the ἀφεδρών, or draught, Purging all meats. The most approved reading here is undoubtedly the masculine (καθαρἰζων), and not the neuter (καθαρίζον). This change of reading compels a somewhat different construction. Accepting, therefore, the masculine as the true reading, the only possible rendering is that which makes this last clause a comment by the evangelist upon our Lord's previous words, in which he indicates to the reader that our Lord intended by this illustration to show that no food, of whatever kind, when received with thanksgiving, can make a man unclean. The clause must, therefore, be connected with the preceding words, by the introduction of the words, in italics, "This he said, making all meats clean." The passage, thus rendered, becomes a very significant exposition of what has gone before. It is well worthy of notice that this explanation is to be found in St. Chrysostom (Homily on St. Matthew 15.): Ὁ δὲ Μάρκος φησὶν ὅτι καθαρίζων τὰ βρώματα ταῦτα ἔλεγεν: "But Mark affirms that he said these things, making the meats clean." It may be added that this explanation agrees finely with the words in Acts 10:15, "What God hath cleansed, that call not thou common."

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.And he saith unto them,.... With some warmth of spirit and resentment, at their stupidity:

are ye so without understanding also? As well as others, and to such a degree; and "yet", as Matthew expresses it, Matthew 15:16, so wretchedly stupid, and so long, and as much, as others:

do ye not perceive? common sense will tell you,

that whatsoever thing from, without entereth into the man, it cannot defile him; See Gill on Matthew 15:16.