1 Corinthians 5:6 in the King James Version
Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump?
Context
5 you are to deliver such a one to Satan for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus.
6 Your boasting is not good. Don’t you know that a little yeast leavens the whole lump?
7 Purge out the old yeast, that you may be a new lump, even as you are unleavened. For indeed Christ, our Passover, has been sacrificed in our place.