Matthew 23:25-26

Now, though they were considered expert interpreters of the fine distinctions of the law, Jesus condemned them as false teachers of the law for hypocritically expanding its intention. While they took offense to His Sabbath healing of a man with a withered hand, He referred to the written law and scorned interpretation based on human reasoning. Jesus claimed their traditions made the word of God void by focusing on minute details, such as tithing of spices, and missing the greater purpose. In Jesus' caricature of them, they cleaned the outside of the drinking cup, but ignored the filth inside it, just as they did their own personal lives and spiritual condition.

The Pharisees were so preoccupied with their external religious practices, that they overlooked their internal hypocrisy within themselves. They remained full of greed and self-indulgence and pride. They missed the truth that cleaning the inside is essential to and required for the cleanliness of the outside. In simple terms, hypocrisy is a spiritually filthy inside with the appearance of a clean outside. To emphasize their insufficient efforts at purity, Jesus called the Pharisees whitewashed tombs that on the outside look beautiful, but on the inside painted an entirely different picture. Physically, they were disguising their spiritual decay.