Beware the Yeast Companion Guide To Matthew 16:

Jesus’ warning about the yeast of the Pharisees and Sadducees was not about bread. It was about the slow, invisible corruption that can work its way into the heart of faith until religion becomes a system we control instead of a relationship that transforms us. The Pharisees leaned toward legalism, performance, and man-made tradition. The Sadducees leaned toward unbelief, compromise, and institutional power. Different roads, same danger: both moved people away from the living God while appearing to protect the things of God. That warning still matters today. Jesus did not expose the yeast to shame His disciples, but to protect them — and to call them into something better: His rest, His truth, His Kingdom, and His freedom.