Christ found a way of penetrating this mask of self-righteousness by a deliberate omission. He knew that the Pharisee would notice this, and he deliberately omitted to wash his hands before the meal, though it is likely that he would normally have done so.
For the self-righteous, all hangs on externals. Even today you get this. Righteousness consists in knowing how to lay table, having a degree of refinement, knowing the correct etiquette. There are many modern examples of self-righteousness – having the right education, or living in a certain area, speaking with the right accent, having inside knowledge of some restricted domain. But external pettiness is widely ridiculed. As Richard Baxter commented, the self-righteous ‘cater for watching eyes, but their consciences are stinking dead.’