"'This people honors me with their lips,
but their heart is far from me;
in vain do they worship me,
teaching as doctrines the commandments of men.'
And exposes that those who thought they were the holy ones are disposing of God's word, ignoring and cancelling out his word in favour of their own authority. They spent their time looking in the mirror to find the wisdom of God and they found whatever they wanted to find.
Jesus applies Isaiah 29v13 to them. The next verses speaks of God doing wonders to destroy the wisdom of the wise. Paul quote that in writing to the Corinthians (1 Corinthians 1v19-24) and identifies Christ himself as the wisdom of God. That's a major problem for the Pharisees. They think they have Jesus exposed but they just set themselves up for the biggest fall of all - The Wisdom of God is looking them in the eye and his name is Jesus. And his gaze penetrates right through to the heart.
The Pharisees, like most of us, thought that sin was circumstantial, and so avoidable by hand washing and the like. Today we think it might be overcome by better education, or money, or by retreat from the dark and dangerous world. Jesus diagnoses differently - the issue is the human heart - a pit of sewage that overflows out of us on a regular basis. And that leaves us in a desperate situation. We cannot fix our hearts. We cannot reform our hearts. We cannot save ourselves. We're lost.
Except, Jesus came into the world for sinners. He loved to be found among them because he came with authority to forgive, secured by his death. My only hope is to believe in Jesus.
Next: the implications of this for missional living.