1 Corinthians 5:6-8

61Your boasting is not good. 2Do you not know that 3a little 4leaven leavens the whole lump of dough? 7Clean out the old leaven so that you may be a new lump, just as you are in fact unleavened. For Christ our 5Passover also has been sacrificed. 8Therefore let’s celebrate the feast, 6not with old leaven, nor with the leaven of malice and wickedness, but with the unleavened bread of sincerity and truth.