'Beware of the Leaven' in the Bible

And Jesus said to them, Take heed, and beware of the leaven of the Pharisees and Sadducees.

How is it that ye do not understand, that I spoke not to you of loaves? But [I said] Beware of the leaven of the Pharisees and Sadducees.

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

And he charged them, saying, Take heed, beware of the leaven of the Pharisees, and the leaven of Herod.

In the mean time, when the multitude was gathered together in myriads, so that they trod one upon another, he began to say to his disciples first, Beware of the leaven of the Pharisees, which is hypocrisy.