So, we should observe the Festival [i.e., live the Christian life], but not with the old yeast [i.e., old sinful ways], such as the leavening [effect] of evil and wickedness, but with the unleavened bread of sincerity and truth.

Get rid of the old yeast [i.e., of sin, and especially the unrepentant sinner], so that you can be a new batch of dough, without yeast in it [i.e., a godly church without unrepentant sinners in it] as [I know] you really are. For our Passover [Lamb], Christ, has already been sacrificed.

Your boasting is not good. Do you not know that a little yeast can leaven the whole batch of dough?