1 Corinthians 5:8

⁶  Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump?

⁷  Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us:

⁸  Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth.

⁹  I wrote unto you in an epistle not to company with fornicators:

¹⁰  Yet not altogether with the fornicators of this world, or with the covetous, or extortioners, or with idolaters; for then must ye needs go out of the world.