Church Fathers on Matthew 23:25

In different words, but to the same purport as before, He reproves the hypocrisy and dissimulation of the Pharisees, that they shewed one face to men abroad, but wore another at home. He means not here, that their scrupulousness respecting the cup and the platter was of any importance, but that they affected it to pass off their sanctity upon men; which is clear from His adding, 'but inwardly ye are full of ravening and uncleanness.'

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…

He therefore is reproving those who, pursuing an ostentation of useless scrupulosity, neglected the discharge of useful morality. For it is the inside of the cup that is used; if that be foul, what profit is it to cleanse the outside? And therefore what is needed is purity of the inner conscience, that those things which are of the body may be clean without.