Leaven, or yeast, is a living fungus that permeates everything. It's in our food, in the ground beneath our feet, in the very air we breathe. It's known for it's ability to multiply and spread. This makes it a fitting metaphor for the false teaching that surrounds us everywhere and also multiplies and spreads. The best defense against false teaching is discernment, the ability to differentiate right from wrong, truth from error. Sadly, a lack of discernment is commonplace - in Jesus' day, and in the church today - a condition that can only be reversed by diligent knowledge and application of God's word. An expository sermon from Matthew 16:1-12.