I Corinthians 5:7-8 - Purge out therefore the old leaven

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:

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.

-- I Corinthians 5:7-8 KJV