Beware the leaven of the Pharisees

Not the same place in gospel of Matthew as this below, but to me, it is very close to the same thing.

Woes to Scribes and Pharisees
…26"You blind Pharisee, first clean the inside of the cup and of the dish, so that the outside of it may become clean also. 27"Woe to you, scribes and Pharisees, hypocrites! For you are like whitewashed tombs which on the outside appear beautiful, but inside they are full of dead men's bones and all uncleanness. 28"So you, too, outwardly appear righteous to men, but inwardly you are full of hypocrisy and lawlessness

People worry more about appearances than the reality.  What is inside matters more than its appearance, but for many people it seems to be the other way around.