John Chrysostom
Note, that speaking of tithes He said, These things ought ye to have done, and not to leave the other undone: for tithes are a kind of alms, and what wrong is it to give alms? Yet said He it not to enforce a legal superstition. But here, discoursing of things clean and unclean, He does not add this, but distinguishes and shews that external purity of necessity follows internal; the outside of the cup and platter signifying the body, the inside the soul.
Or, He means that the Jews whenever they were to enter the temple or to offer sacrifice, or on any festivals, used to wash themselves, their clothes, and their vessels, but none cleansed himself from his sins; but God neither commends bodily cleanliness, nor condemns the contrary. But suppose foulness of person or of vessels were offensive to God, which must become foul by being used, how much more does He not abhor foulness of conscience, which we may, if we will, keep ever pure?
This He speaks not of the cup and platter of sense, but of that of the understanding, which may be pure before God, though it have never touched water; but if it have sinned, then though the water of the whole ocean and of all rivers have washed it, it is foul and guilty before God.