Tradition, Corban, and the Defilement of the Heart
Pharisees and scribes challenge Jesus because some disciples eat without the customary handwashing. Jesus quotes Isaiah 29:13 about honoring God with lips while the heart is far away, then gives the Corban example: a religious dedication could be used to evade the command to honor father and mother. He moves the discussion from external contact to the heart, listing evils that arise from within.
Where this fits in the story: Mark distinguishes Scripture from human tradition without suggesting that every tradition is automatically evil. Jesus’ accusation is specific: a tradition becomes corrupt when it nullifies God’s command while claiming religious honor.