Matthew 16:1, 6, 12

And the Pharisees and Sadducees came, and to test him they asked him to show them a sign from heaven.

Jesus said to them, “Watch and beware of the leaven of the Pharisees and Sadducees.”

Then they understood that he did not tell them to beware of the leaven of bread, but of the teaching of the Pharisees and Sadducees.