“To eat with unwashed hands does not defile a man.” Let us learn then what are the things that defile the person. Let us learn them and flee from them. For even in the church we still see such a custom prevailing among many that gives great attention to what we are wearing and whether we have our hands washed. But as to presenting a clean soul to God, they make no account. I say wash to what degree is fitting, but above all wash with virtues and not with water only. No one is forbidding the washing of the hands or mouth, but the real filth of the mouth is evil speaking, blasphemy, reviling, angry words, filthy talking, inordinate laughter and immature jesting. If you are not conscious of yourself doing these things or of being defiled with this filth, then draw near with confidence. But if you have often done these things and received these stains, why do you think that washing your tongue with water is going to change anything? You labour in vain to wash it out externally, while you are still inwardly carrying such deadly and hurtful filth.
Saint John Chrysostom, The Gospel of Matthew, Homily 51. 4-5, in Manlio Simonetti (ed). Matthew 14-28 (Ancient Christian Commentary on Scripture) 26.