The Leaven of the Pharisees and Sadducees

And when His disciples came to the other side, they had forgotten to take bread. Then Jesus said unto them, Take heed and beware of the leaven of the Pharisees and of the Sadducees. And they reasoned among themselves, saying, is it because we have taken no bread. When Jesus perceived, He said unto them, O you of little faith, why reason you among yourselves, because you have brought no bread? Do you not yet understand, nor remember the five loaves of the five thousand and how many baskets you took up? Neither the seven loaves of the four thousand and how many baskets you took up? How is it that you do not understand that I spake not to you concerning bread but that you should beware of the leaven of the Pharisees and of the Sadducees? Then they understood how He bade them not to be aware of the leaven of bread but of the doctrine of the Pharisees and of the Sadducees. Matthew 16 vs 5-12.