Galatians 5:9

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, It is because we have taken no bread. Which when Jesus perceived, he said unto them, O ye of little faith, why reason ye among yourselves, because ye have brought no bread? Do ye not yet understand, neither remember the five loaves of the five thousand, and how many baskets ye took up? Neither the seven loaves of the four thousand, and how many baskets ye took up? 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 understood they how that he bade them not beware of the leaven of bread, but of the doctrine of the Pharisees and of the Sadducees.

Ye serpents, ye generation of vipers, how can ye escape the damnation of hell?

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.

It is like leaven, which a woman took and hid in three measures of meal, till the whole was leavened.

Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump?

Be not deceived: evil communications corrupt good manners.