'Leaven of the Pharisees' in the Bible

Then Jesus said unto them, Take heed and beware of the leaven of the Pharisees and of the Sadducees.

How is it that ye do not understand that I spake it not to you concerning bread, that ye should beware of the leaven of the Pharisees and of the 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 of the leaven of Herod.

In the mean time, when there were gathered together an innumerable multitude of people, insomuch that they trode one upon another, he began to say unto his disciples first of all, Beware ye of the leaven of the Pharisees, which is hypocrisy.