1 Corinthians 5:6-7

6Your boasting about this is terrible. Don’t you realize that this sin is like a little yeast that spreads through the whole batch of dough?

7Get rid of the old “yeast” by removing this wicked person from among you. Then you will be like a fresh batch of dough made without yeast, which is what you really are. Christ, our Passover Lamb, has been sacrificed for us.