Matthew 16:12
Then they understood that He meant, guard yourselves not against yeast for bread, but against the teaching of the Pharisees and the Sadducees.
Luke 12:1
Meanwhile as the people had gathered in tens of thousands, so that they were trampling upon one another, He began to say, first of all, to His disciples: "Beware of the yeast of the Pharisees, that is, hypocrisy.
Acts 12:3
and when he saw that this was agreeable to the Jews, he proceeded to arrest Peter too -- it was at the time of the feast of Unleavened Bread.
1 Corinthians 5:7-8
You must clean out the old yeast, that you may be a fresh lump, as you are to be free from the old yeast. For our Passover Lamb, Christ, has already been sacrificed.
Galatians 5:12
I almost wish that these men who are upsetting you would go all the way, and have themselves mutilated.