Matthew 16:1, 6, 12

One day some of the Pharisees and those of the Jewish sect known as the Sadducees approached Jesus, insisting that he prove to them that he was the Messiah. “Show us a supernatural sign from heaven,” they demanded.

Jesus spoke up and said, “Watch out for the yeast of the Pharisees and the Sadducees.”

Then finally they realized he wasn’t talking about yeast found in bread, but the error of the teachings of the Pharisees and the Sadducees.