1 Corinthians 5:6-11

Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump? Purge out the old leaven, that ye may be a new lump, even as ye are unleavened. For our passover also hath been sacrificed, even Christ: wherefore 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. I wrote unto you in my epistle to have no company with fornicators; not at all meaning with the fornicators of this world, or with the covetous and extortioners, or with idolaters; for then must ye needs go out of the world: but as it is, I wrote unto you not to keep company, if any man that is named a brother be a fornicator, or covetous, or an idolater, or a reviler, or a drunkard, or an extortioner; with such a one no, not to eat.