Matthew 15:17 - Ellicott's Commentary On The Whole Bible

Is cast out into the draught. — The word is used in its old English meaning, as equivalent to drain, sewer, cesspool (see 2 Kings 10:27). St. Mark (Mark 7:19) adds the somewhat perplexing words, “purging all meats,” on which see Note on that verse. The principle implied is that a process purely physical from first to last cannot in itself bring any moral defilement. It was possible, of course, that the appetites connected with that process might bring the taint of moral evil; but then these appetites were there before the food, and they took their place among the things that came “out of the heart,” and not into it.