1 Cor 5:6-8

6^d Your boasting is not appropriate. Do you not know that a little yeast^* leavens all the dough? 7^* Clear out the old yeast, so that you may become a fresh batch of dough, inasmuch as you are unleavened. For our paschal lamb, Christ, has been sacrificed.^e 8Therefore, let us celebrate the feast, not with the old yeast, the yeast of malice and wickedness, but with the unleavened bread of sincerity and truth.^f