1 Corinthians 5:7-8

5:7 Clean out the old yeast so that you may be a new batch of dough – you are, in fact, without yeast. For Christ, our Passover lamb, has been sacrificed. 5:8 So then, let us celebrate the festival, not with the old yeast, the yeast of vice and evil, but with the bread without yeast, the bread of sincerity and truth.