To the Jews leaven was a sign of evil. It was a piece of dough from left-over bread which fermented. Fermentation was associated with decay and rotting – the state of foul-smelling decomposition. Why did Jesus warn his disciples to avoid the ways of the Pharisees? The Pharisees wanted everyone to recognize that they were pious and good Jews because they meticulously and scrupulously performed their religious duties. Jesus turned the table on them by declaring that outward appearace doesn't always match the inward intentions of the heart. Anyone can display outward signs of goodness while inwardly harboring evil thoughts and intentions. The word hypocrite means actor – someone who pretends to be what he or she is not. But who can truly be good, but God alone? Hypocrisy thrives on making a good appearance and masking what they don't want others to see. The good news is that God's light exposes the darkness of evil and sin in our hearts, even the sin which is unknown to us. And God's light transforms our hearts and minds and enables us to overcome hatred with love, pride with humility, and pretense with integrity and truthfulness. God gives grace to the humble and contrite of heart to enable us to overcome the leaven of insincerity and hypocrisy in our lives.