"First clean the inside of the cup and dish, and then the outside also will be clean."
Matthew 23:26
In Matthew 23, Jesus delivers his most confrontational teaching. He is speaking to the Pharisees — the most religiously observant people of his day.
The Pharisees had mastered the outside of the cup. Their external behaviour was impeccable. But Jesus saw what they had missed: that God is not primarily interested in behaviour.
Jesus is not against righteous behaviour. He is against the order of operations. Clean the inside, and the outside takes care of itself.
We are not called to scrub ourselves clean through effort and discipline. We are invited to bring the dirty cup to Jesus and let him clean it.
"Create in me a pure heart, O God, and renew a steadfast spirit within me."
Psalm 51:10