Not that which goeth into the mouth, &c. We must heartily pity and pray to God for those who blindly pretend from hence, that to eat any kind of meats, or as often as a man pleaseth on fasting-days, can defile no man. (Witham)

No uncleaness in meat, nor any dirt contracted by eating it with unwashed hands, can defile the soul; but sin alone, or a disobedience of the heart to the ordinance and will of God. And thus, when Adam took the forbidden fruit, it was not the apple which entered into his mouth, but the disobedience to the law of God, which defiled him. The same is to be said if a Jew, in the time of the old law, had eaten swine’s flesh; or a Christian convert, in the days of the apostles, contrary to their ordinance, had eaten blood; or if any of the faithful, at present, should transgress the ordinance of God’s Church, by breaking the fasts: for in all these cases the soul would be defiled, not indeed by that which goeth into the mouth, but by the disobedience of the heart, in wilfully transgressing the ordinance of God, or of those who have their authority from him. (Challoner)

Jesus Christ by no means prohibits fasting and abstinence from certain food, and at certain times, or he would have been immediately accused of contradicting the law; he only says, that meat which they esteem unclean does not of itself, and by its own nature, defile the soul; which is what the Pharisees (and before them Pythagoras, and after them the Manicheans) maintained, and which St. Paul warmly confutes. (1 Timothy iv. 4) (Tirinus)

If a man gets intoxicated, adducing this same plea, that what entereth by the mouth, &c. is not the answer obvious; that it is not the wine, but the intemperance, contrary to the law of God, which defileth him: for drunkards shall not possess the kingdom of God. (1 Corinthians vi. 10)